Daniel sent us this one — he wants a practical primer on wall types for home renovations, specifically how to pick the right drill bit and anchor so your shelf actually stays on the wall instead of crashing down at three in the morning. And he mentioned the uniquely Israeli flavor of this problem, where you've got drywall in rentals, concrete in older buildings, and no idea what's behind the paint. I've been there. I once tried to hang a spice rack in a Jerusalem rental and ended up with what I can only describe as a peephole into my neighbor's apartment.
I drilled into what I thought was drywall in a Tel Aviv flat and hit a steel beam. The bit snapped, the drill kicked back, and I spent the rest of the afternoon at the hardware store explaining to the guy why I needed a single six-millimeter masonry bit and a bandage. He wasn't impressed.
The ironmonger in the shuk would've understood.
The ironmonger in the shuk is a consultant. The chain store is just a fulfillment center. But you're right — and this is exactly the season for this conversation. We're in late May, post-Pesach, everyone's got that renovation energy before the summer heat kicks in, and thousands of people are about to pick up a drill and make mistakes that cost them time, money, and a fist-sized hole in the living room wall.
Let's start with the fundamental question — what are you actually drilling into? Because in Israel, the answer is never as simple as it looks.
It's harder here than in the US or UK for a very specific reason. In most countries, construction is relatively consistent by era — you know what you're getting. In Israel, we have this hybrid mess. Pre-nineteen-nineties buildings are almost entirely reinforced concrete, what's called Yitzchaki-style construction. Then the nineties through the twenty-tens saw a boom in hollow concrete blocks — ITONG, Ytong, aerated autoclaved concrete. And post-twenty-ten, new builds increasingly use drywall, or what we call Gipson here, for interior partitions, especially in rentals where developers are cutting costs.
The rental market makes this worse because tenants don't know what's behind the paint. The landlord painted over everything six times before you moved in, and now you're staring at a wall that could be concrete, could be hollow block, could be drywall, could be plaster over brick from the British Mandate era.
There was actually a discussion in a local DIY forum I follow — a guy in a nineteen-ninety-five Ramat Gan apartment tried to hang a bookshelf. He assumed drywall. Used a drywall anchor. It spun in the hole. He upsized to a bigger plastic anchor. He went bigger again. Ended up with a hole the size of his fist. Turns out it was ten centimeters of hollow block behind two centimeters of plaster. The fix was a toggle bolt with a ten-millimeter masonry bit on rotary-only mode. But he learned the hard way.
The hard way is expensive. So what's the single biggest mistake people make when they grab a drill?
They don't identify the wall first. They just assume. They grab whatever bit is in the drill case, whatever anchor is in the junk drawer, and they go for it. And that works right up until it doesn't — at which point you're patching drywall or worse, you've hit rebar and now you need a new drill bit and possibly a new wrist.
The core thesis here is: there are exactly three wall types you need to be able to identify, and each demands a different drill bit, a different anchor, and a different technique. Get the identification right and everything else follows.
And by the end of this segment, you'll know the three-second test to identify any wall in your apartment. But let's get into the three types first, because the test makes more sense once you understand what you're listening for.
Alright, let's get into the three wall types you'll encounter. I'm going to teach you the tap test, and then we'll break down each one.
Wall type one: reinforced concrete, or what we call beton here. This is your pre-nineteen-nineties building, your load-bearing walls, your bomb shelter room — the mamad. Israeli concrete from that era has an average compressive strength of twenty to twenty-five megapascals, which is C-twenty-slash-twenty-five grade. That's actually harder than typical European domestic concrete. This stuff is not messing around.
How do you identify it before you drill?
The tap test. Take your knuckle and rap on the wall. Concrete produces a solid, high-pitched thunk with no resonance. It feels dense. It feels like you're knocking on a mountain. If you do a test drill — and I mean just barely breaking the surface — you'll get grey dust. Not white, not crumbly beige.
The bit you need?
Carbide-tipped masonry bit. This is non-negotiable. A standard HSS bit — high-speed steel — will burn up in seconds against Israeli concrete. That's the number one mistake I see. People grab the shiny silver bit from the set and wonder why it's smoking. Carbide-tipped, always.
The anchor situation?
Depends on the load. For light loads — picture frames, small mirrors, things under ten kilos — a simple nylon plug, what everyone calls a Rawl plug, works perfectly if the hole is exactly the right diameter. For heavy loads — shelving units, TVs, anything above ten kilos — you want sleeve anchors or wedge anchors. And for really heavy stuff, above fifty kilos, you go chemical anchor, which we'll get to.
What about technique?
Use hammer drill mode. The hammer action is essential for concrete — it's what breaks the aggregate so the bit can advance. But here's the key: start slow. If you go full speed immediately, the bit will wander and your hole will be in the wrong spot. Start slow to establish a guide dimple, then ramp up. And once you've drilled the hole, blow out the dust before inserting the anchor. I mean really blow it out. Use a straw, use compressed air, use your lungs — but get that dust out. Dust is the enemy of grip.
I've seen people skip that step and then wonder why the anchor pulls out. It's like trying to set a tent stake in loose sand.
The dust acts as a lubricant between the anchor and the wall. You want friction, not lubrication. Now, a six-millimeter nylon plug in concrete can hold approximately twenty kilos in shear — that's downward force, like a shelf pulling down. But it only holds about eight kilos in tension — that's pull-out force, like someone grabbing the shelf and yanking. That's why shelves fail when people pull down on them. The load shifts from shear to tension and suddenly your anchor is past its limit.
Concrete is straightforward enough. Solid wall, hammer drill, masonry bit, right anchor for the weight. What about wall type two?
Hollow concrete block. ITONG, Ytong, aerated autoclaved concrete. This is the one that tricks people the most. These blocks were huge in the nineties through the twenty-tens for interior walls. They're lightweight, they're porous, and they have a compressive strength of only two to four megapascals — that's about one-tenth of concrete. They are soft. And that softness is the trap.
Because people treat it like solid concrete.
They see a greyish wall, they grab the masonry bit and the hammer drill, and they go to town. And the hammer action just pulverizes the block from the inside. The aggregate is too soft — instead of breaking cleanly, it crumbles. Your hole ends up oversized and irregular, and no anchor in the world will grip properly.
What's the identification for hollow block?
The tap test again. Where concrete gives you a high-pitched thunk, hollow block gives you a dull, hollow thud. It's noticeably different. It sounds empty. If you tap concrete and then tap hollow block, you'll never confuse them again. The block is also lighter — if you're near an exposed edge somewhere, like inside a closet, you can sometimes feel the difference in density.
Here's the thing — you can use the same carbide-tipped masonry bit, but you must use rotary-only mode. The vibration is what destroys the block. A sharp masonry bit on rotary mode will cut cleanly. And the anchor is where things get really different.
Because a standard nylon plug won't grip that porous material.
The walls of the hole are too crumbly for friction-based anchors. You need something that expands behind the face of the block. Cavity-wall anchors, also called butterfly anchors or toggle bolts — these have wings that open up inside the hollow cavity and brace against the back of the block face. For lighter loads, there are coarse-thread plastic anchors specifically designed for aerated concrete. The Fischer UX series is the most commonly sold anchor in Israeli hardware stores for exactly this purpose. The Fischer UX eight-by-fifty has a rated pull-out strength of zero point five kilonewtons in aerated concrete — that's about fifty kilos.
Fifty kilos is a lot for something going into what's basically fancy cinderblock.
It is, but that rating assumes perfect installation — right bit size, right depth, no dust, no crumbling. In practice, you want a safety margin.
Alright, wall type three: drywall.
The bane of every renter's existence. Drywall is increasingly common in post-twenty-ten builds and especially in rental renovations where the landlord wanted to split a room or add a partition cheaply. It's plasterboard mounted on steel studs. The tap test gives you a crisp, papery thwack — very distinctive. It sounds like you're knocking on a cardboard box.
There's a second test for this one.
The magnet test. Drywall itself isn't magnetic, but the steel studs behind it are. Take a rare-earth magnet — the kind you can get at any hardware store for a few shekels — and run it along the wall. If it sticks, you've found a stud. The standard spacing for steel studs in Israeli drywall construction is sixty centimeters on center, matching European standards. That's different from the US, which uses sixteen inches — about forty point six centimeters. So if you're watching American DIY videos, the stud spacing advice won't match.
This is where people really mess up. They use a standard plastic anchor, it spins uselessly in the cavity, and they keep drilling bigger holes hoping that'll fix it.
The spiral of despair. For drywall, the anchor situation breaks down by weight. For light loads — picture frames, small decor, under ten kilos — use self-drilling drywall anchors. These are the ones with the sharp screw tip that bite directly into the board. No pre-drilling needed in most cases. For medium loads — shelves, medium mirrors, ten to twenty-five kilos — you want toggle bolts or what are sometimes called Molly bolts. These expand behind the board and distribute the load across a wider area.
For anything heavy?
You must hit a steel stud. Never hang more than about fifteen kilos on drywall alone. If you're mounting a cabinet or a TV, find the studs with your magnet, mark them, and drive your toggle bolts or heavy-duty screws directly into the steel. A toggle bolt into a steel stud can hold fifty kilos or more. The same toggle bolt in just drywall might hold twenty-five — and that's if everything goes perfectly.
I remember a case — someone in a twenty-eighteen Tel Aviv new-build tried to hang a forty-kilo mirror on drywall using four self-drilling anchors rated for ten kilos each. On paper, forty kilos of capacity for a forty-kilo mirror. The mirror fell after three days.
Because the ratings are for shear load in ideal conditions. A mirror hanging on a wall is mostly shear, but there's always some tension component — the mirror isn't perfectly flush, someone bumps it, the wall settles. Those four anchors were probably each experiencing more than ten kilos of real-world force. Plus, self-drilling anchors in drywall lose strength over time as the board flexes. The fix in that case was locating the steel studs — they were sixty centimeters apart, standard — and using toggle bolts into the studs. Mirror's still up two years later.
We've covered the three wall types and their ideal anchors. But what about the real-world complications — like when you're in a rental and the landlord painted over everything?
This is the Israeli rental wildcard. Landlords here will paint over anything. Old tiles, crumbling plaster, exposed concrete, previous tenants' mistakes — it all gets the same coat of off-white and you're supposed to figure it out. Visual identification becomes impossible because everything looks the same.
You can't see what you're drilling into. What do you do?
The magnet and tap combo. Use a rare-earth magnet to scan the wall. If the magnet sticks in a regular pattern — every sixty centimeters — you've got drywall on steel studs. If the magnet sticks everywhere, not in a pattern, you might have metal lath under plaster, which was common in older construction. If the magnet sticks in a few random spots, you're probably hitting rebar in concrete.
Then you confirm with the tap test.
If the magnet sticks in a stud pattern and the tap sounds hollow and papery, it's drywall. If the magnet sticks randomly and the tap is solid and high-pitched, it's concrete with rebar. If the magnet doesn't stick at all and the tap is dull and hollow, it's hollow block. If the magnet sticks everywhere and the tap has a slightly metallic ring, it's plaster over metal lath — which is its own special nightmare.
Plaster over metal lath. The wall type that laughs at your anchor selection.
It really does. You basically treat it like concrete but with extra caution about hitting the lath. If you're drilling and you suddenly feel resistance change and hear a metallic scraping, stop immediately. You've hit the lath. Move your hole.
Let's talk about bit selection more broadly. What's the minimum kit someone needs?
That's it. You don't need a fifty-piece set. You need a six-millimeter carbide-tipped masonry bit for concrete and hollow block, a five-millimeter HSS bit for drilling into steel studs when you need to mount toggle bolts, and a three-millimeter wood bit for the rare occasions you encounter wooden studs — they're uncommon in Israel but they do exist in some older builds, particularly in Jerusalem.
What about those universal bits that claim to do everything?
They do nothing well. A bit designed to cut wood, metal, and masonry simultaneously is a compromise in every direction. It'll cut masonry slowly and dull quickly, it'll tear wood instead of cutting it cleanly, and it'll overheat in metal. Spend fifty shekels on three decent bits from Ace or Home Center instead of fifteen shekels on a multi-bit set from the bargain bin.
The ironmonger in the shuk would agree.
The ironmonger in the shuk would sell you exactly those three bits and throw in a free magnet. So let me run through the anchor selection cheat sheet, because this is what people really need to internalize. For concrete: nylon plug, what everyone calls a Rawl, up to ten kilos. Sleeve anchor up to fifty kilos. Wedge anchor above fifty kilos. For hollow block: cavity anchor, the butterfly type, or the Fischer UX series for lighter loads. For drywall: self-drilling anchor up to ten kilos, toggle bolt up to twenty-five kilos on drywall alone, and if you're into a steel stud, fifty kilos or more.
There's one more option you mentioned — chemical anchors.
Chemical anchors, also called epoxy anchors. You drill the hole, clean it obsessively, inject a two-part epoxy, and insert a threaded rod. Once it cures — usually twenty-four hours — it's stronger than the concrete around it. The Rawl R-KEM system is the one you'll find in Israeli hardware stores. It's overkill for most home applications, and it's permanent — you'll never get that rod out. But for something like a heavy safe or a pull-up bar mounted to concrete, it's the gold standard.
The trade-off being cure time versus instant hold.
A mechanical wedge anchor is instant — you tighten it and it's done. A chemical anchor needs a full day to cure before you can load it. For most home use, mechanical is fine. Chemical is for when you absolutely cannot afford failure.
Now let's talk about the failure modes, because this is where people get frustrated and start making things worse. The anchor spins in the hole.
One, the hole is too big. You used a bit that's larger than the anchor spec. The fix is to use the exact bit size printed on the anchor package — if it says six millimeters, use six millimeters, not six point five. Two, the hole is too shallow. The anchor protrudes and can't seat properly. Drill five millimeters deeper than the anchor length. Three, dust in the hole. The anchor can't grip because there's powder between it and the wall. Blow it out. Four, wrong anchor for the wall type. You used a nylon plug in drywall and it's just spinning in the cavity. Identify the wall first.
The biggest mistake people make when the anchor spins?
They reach for a bigger anchor. This is the number one cause of wall damage I see. If an anchor spins, the instinct is to grab a larger one, drill the hole bigger, and try again. But if the wall can't grip a six-millimeter anchor, it won't grip an eight-millimeter anchor either — you've just made a bigger hole that's harder to patch. Stop, identify the wall, and switch to the correct anchor type.
What about when you're drilling and you hit something hard that isn't concrete?
You've probably hit rebar or metal lath. If you keep drilling, you'll dull your bit and potentially damage the rebar, which is structural. Move your hole a few centimeters up or to the side. If you keep hitting metal everywhere, you might have metal lath — in that case, use a metal-cutting bit to get through the lath, then switch back to masonry for the substrate behind it. But honestly, if you're hitting lath, call someone who's done it before. It's easy to make a mess.
Patching mistakes — let's cover that quickly, because people are going to make holes they regret.
For drywall, use a drywall repair patch and spackle. The mesh patches work well — you stick them over the hole, spackle over them, sand, paint. For small holes, you can just fill with joint compound. For concrete, use hydraulic cement — it expands slightly as it cures and locks into the hole. For hollow block, use a mesh patch and joint compound, but be aware that the patch will always be weaker than the surrounding material.
If you're patching hollow block, don't plan to drill into the same spot again.
The patch is cosmetic, not structural. If you need to mount something where you previously made a mistake, move the hole.
Let me throw a curveball at you. What if the wall has metal lath under plaster and the magnet sticks everywhere? How do you distinguish that from drywall on steel studs?
Drywall on steel studs produces a regular magnetic pattern — stick, no stick, stick, no stick, every sixty centimeters. Metal lath produces a continuous magnetic field — the magnet sticks everywhere, or nearly everywhere, because the entire wall is covered in a metal mesh. Plus the tap sound is different. Drywall sounds hollow and papery. Plaster over lath sounds harder, more solid, with a slight metallic ring to it. It's subtle but once you've heard both, you can tell.
The magnet pattern is the real tell.
The magnet pattern plus the tap. Together they'll identify basically any wall you encounter. And that's really the core skill here — before you even pick up a drill, you should know what you're dealing with.
Let's distill all of this into a simple decision tree you can use every time you pick up a drill.
I love a good decision tree. Here it is. Step one: tap the wall with your knuckle. Concrete gives you a high-pitched thunk. Hollow block gives you a dull thud. Drywall gives you a papery thwack. Those three sounds — thunk, thud, thwack — are your primary identification tool. If you remember nothing else, remember the three sounds.
Confirm with a magnet. If it sticks in a regular sixty-centimeter pattern, you've got drywall on steel studs. If it sticks randomly, you've got concrete with rebar. If it doesn't stick at all, you've got hollow block or plain concrete. If it sticks everywhere, you might have metal lath.
Step three: select your bit. Carbide-tipped masonry bit for concrete and hollow block. HSS bit for steel studs. Wood bit for wooden studs.
Step four: select your anchor based on wall type and load. Concrete: nylon plug for light, sleeve or wedge anchor for heavy. Hollow block: cavity anchor or Fischer UX. Drywall: self-drilling anchor for light, toggle bolt for medium, toggle bolt into stud for heavy.
Step five: set your drill mode. Hammer mode for concrete. Rotary-only for hollow block and drywall. And step six: blow out the dust before inserting the anchor.
That's the flowchart. Tap, magnet, bit, anchor, mode, dust. Six steps, about thirty seconds of thinking, and you'll never guess at a drill bit again.
Here's a practical tip I want people to actually do. Go to your wall right now — or after the episode — do the tap test, identify the type, and write it on a piece of masking tape. Stick that tape to the back of your light switch plate. Next time you need to drill, pop off the plate, read the tape, and you know exactly what you're dealing with. No guessing, no remembering, no mistakes.
That's brilliant. The light switch plate is the perfect hiding spot — it's accessible, it's invisible, and you'll never lose it. I'm going to do that in my own apartment.
You don't already know what your walls are?
I know what they are, but I'd still write it down. Masking tape doesn't.
Let's hit the key takeaways. Number one: the three-second wall identification test. Tap with your knuckle — thunk is concrete, thud is hollow block, thwack is drywall. Confirm with a magnet. That's it.
Number two: the three-bit starter kit. Six-millimeter carbide masonry bit, five-millimeter HSS bit, three-millimeter wood bit. Buy them from a hardware store, not a general store. Spend fifty shekels, not fifteen. Your walls will thank you.
Number three: the anchor decision tree. Concrete gets nylon plugs or wedge anchors. Hollow block gets cavity anchors. Drywall gets self-drilling anchors or toggle bolts into studs. Never use a standard plastic anchor in drywall or hollow block. It will fail.
Number four: if an anchor spins, stop. Don't reach for a bigger one. Identify the wall, check your bit size, check your anchor type, and start over. The hole you already made can be patched. The bigger hole you're about to make is harder to fix.
I also want to add one thing that doesn't get said enough: measure twice, drill once, and always blow out the dust. The dust thing seems minor but it's the difference between an anchor that holds twenty kilos and an anchor that pulls out at five.
It really is. Dust reduces friction by creating a barrier between the anchor and the wall. In concrete, that's a twenty-kilo anchor becoming an eight-kilo anchor. In hollow block, it's even worse because the material is already porous.
To wrap up, here's the one thing we want you to remember — and a challenge for you.
The challenge: go find the weirdest wall in your apartment. The one that doesn't match any of the three types we described. The one that sounds different, or has something unexpected behind it. Send us a voice memo about it. We might feature it in a future episode. I'm genuinely curious what people are living with out there.
I once encountered a wall in a Jerusalem apartment that was stone on one side, hollow block on the other, and drywall in the middle where someone had patched a doorway. Three wall types in a single surface. That's the kind of thing we want to hear about.
Looking forward, this whole identification game is going to change again. Israeli construction is moving toward more prefabricated and modular methods — there are pilot projects with three-D-printed concrete walls starting to appear, and those have completely different properties. We'll cover that in a future episode when the technology is more widespread.
If you found this useful, leave a five-star review on Apple Podcasts or Spotify. It helps other DIYers find the show, and it helps us keep doing this. And remember: measure twice, drill once, and always blow out the dust.
This has been My Weird Prompts, produced by Hilbert Flumingtop. Find us at myweirdprompts dot com or wherever you get your podcasts.
And now: Hilbert's daily fun fact.
Hilbert: The earliest phonograph recording media used a thin optical layer of lampblack — essentially soot — on a glass cylinder. When a stylus traced sound vibrations through the soot, the varying transparency of the groove could be read by a beam of light. An optical audio format, invented in the eighteen-eighties, decades before the vinyl record existed.
Vinyl's great-grandfather was literally dirt on glass. That feels right somehow.
