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If you’ve spent any time shopping for lock picks, you’ve hit the thickness question. The numbers are small — we’re talking thousandths of an inch — but the difference between them matters more than beginners expect.

Get it wrong and you’ll either be forcing picks into locks where they don’t belong, or swimming in a keyway so wide your pick is doing nothing useful. Get it right and everything just… works better.

Here’s a plain-English breakdown of each thickness, what it’s for, and which one you should actually start with in Australia.

First — What Is “Thou”?

“Thou” is short for thousandths of an inch. So 15thou = 0.015″, 20thou = 0.020″, 23thou = 0.023″. It refers to the thickness of the pick blade — the flat metal part that goes into the keyway.

Thicker picks are stiffer and stronger. Thinner picks are more flexible and fit narrower keyways. Neither is universally better — it depends entirely on the lock you’re picking.

The Thicknesses: What Each One Actually Does

23thou — The Australian All-Rounder

If you’re picking locks in Australia, 23thou is almost always the right starting point.

Why? Because Australian locks skew towards larger, more open keyways. The Lockwood C4 — one of the most common cylinders you’ll find on Australian doors — has a wide keyway that works perfectly with 23thou. It’s thick enough to give you solid feedback and control, but slim enough to navigate medium keyways without drama.

The other advantage of 23thou as a starting point: it covers the middle ground between wide and narrow, meaning you don’t immediately need a second set. One thickness, most Australian locks, sorted.

Best for: Lockwood cylinders, standard Australian padlocks, most door locks you’ll encounter day-to-day.

Browse Bare Bones 23thou picks →

20thou — The Step Down

20thou sits between 23thou and 15thou — thinner and more flexible, but still substantial enough to feel what’s happening inside the lock.

Once you’re comfortable with 23thou and want to start picking medium-profile keyways more precisely, 20thou becomes useful. It’s also where you start if you’re picking locks that 23thou feels tight in — the pick is just cramped in there and you’re losing feedback.

A lot of intermediate pickers run both 20thou and 23thou, choosing based on the specific lock in front of them. For Australian pickers, 20thou becomes relevant when you start exploring a wider variety of locks beyond the standard Lockwood-style cylinders.

Best for: Medium keyways, transitioning from beginner to intermediate, locks where 23thou feels slightly cramped.

Browse Bare Bones 20thou picks →

15thou — The Specialist

15thou is thin. Genuinely thin. It flexes noticeably and requires more finesse to control — which is exactly the point, because the locks it’s designed for demand it.

European locks — brands like ABUS, Mul-T-Lock, and other high-security cylinders — often have narrow, complex keyways that simply won’t accept a 23thou or 20thou pick without making contact with the keyway walls constantly. That contact kills your feedback and makes single pin picking nearly impossible.

15thou cuts through narrow keyways cleanly and lets you feel what’s actually happening with the pins rather than wrestling with the keyway itself.

For Australian beginners, 15thou is not your starting point. But once you’ve got the fundamentals and you start hunting for more challenging locks — particularly anything European — you’ll want it in the kit.

Best for: Narrow European keyways (ABUS, Mul-T-Lock), high-security cylinders, advanced picking where keyway clearance matters.

Browse Bare Bones 15thou picks →

Quick Reference: Which Thickness for Which Lock?

What About 25thou?

You’ll sometimes see 25thou (0.025″) mentioned — it’s a popular thickness with North American brands like Sparrows because it suits North American keyways well. For Australian picking, it’s less universally useful. Our common locks tend to suit 23thou better as the baseline, and 25thou can feel unnecessarily chunky in anything other than the widest keyways.

It’s not useless — but if you’re building an Australian kit from scratch, start with 23thou before considering 25thou.

The Honest Beginner Advice

Don’t buy one of everything. It’s tempting, but you’ll just confuse yourself.

Start with 23thou — hooks and rakes. Pick Australian locks until you can open them reliably. Once you know what you’re doing and you start hitting the limits of what 23thou can get into, that’s when 20thou and 15thou start making sense.

All three thicknesses are available in the Bare Bones shop, made from 301 high-yield stainless steel, and stocked in kits so you don’t have to piece together a set from scratch.

Still not sure which to start with? The Beginner Questions page covers this exact decision in detail — including which kits include which thicknesses and why.

Browse all Bare Bones picks by thickness →