I use utility knives all the time in the shop — opening boxes, trimming prints, cutting filament, breaking down packaging — and I wanted something that felt solid, safe, and predictable, without relying on tiny springs, metal hardware, or complicated internals.

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That’s what led to SLUK: a fully 3D-printed, self-locking utility knife designed around simplicity, reliability, and everyday use.

What Makes SLUK Different

The defining feature of SLUK is right in the name: self-locking.

Instead of a traditional spring-loaded slider or button lock, SLUK uses geometry and friction to lock the blade carrier in position automatically. Once extended, it stays put. When retracted, it stays put. No extra parts, no tiny mechanisms, and nothing to wear out quickly.

It’s a very “3D-printing-native” solution — using shape, tolerance, and material behavior instead of hardware.

Designed for Standard Utility Blades

SLUK is designed around standard utility blades, which are inexpensive, widely available, and easy to replace. The blade is fully enclosed when retracted, and the body provides a comfortable grip without being bulky.

The goal wasn’t to reinvent the utility knife — just to make a clean, functional version that prints well and works reliably.

Printing and Assembly

This design is intentionally straightforward to print and assemble.

• Fully 3D printed
• No supports
• No metal hardware
• Simple press-fit assembly

PLA works well, and PETG or ASA are also good options if you want a bit more durability. As with most functional parts, decent wall thickness matters more than extreme infill.

The tolerances are forgiving, but like most sliding parts, good extrusion consistency helps.

Why I Made This

There are lots of utility knives out there — cheap ones, fancy ones, disposable ones. What I wanted was a printable tool that earns a permanent place in the shop, one that’s easy to understand, easy to maintain, and safe to toss in a drawer or toolbox.

SLUK is the result of that thinking: simple, solid, and designed to work the way you expect it to.

Give It a Try

If you print one and put it to use, I’d love to hear how it holds up for you. Feedback, tweaks, and edge cases are always welcome — that’s how these designs get better over time.

The post SLUK – Self-Locking Utility Knife first appeared on logicalplanet.

Over the last few years, toilet paper manufacturers have been steadily shrinking the inner cardboard core. That doesn’t sound like a big deal… until you realize that a lot of holders (especially simple or minimalist ones) rely on a fairly consistent core size to work properly.

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My original tank-mounted toilet paper holder worked great for years. Then suddenly rolls started falling off, rattling around, or just not fitting the way they used to. That’s what led to this second-generation redesign.

What Changed in Gen 2

The biggest difference in this version is the post itself.

Instead of relying on a rigid diameter that assumes all TP cores are the same, the Gen 2 design uses a compliant, flexible post that adapts to different core sizes — including the smaller modern ones. It grips the roll securely without binding and without needing springs, bearings, or hardware.

The rest of the design stays true to the original goals:

• Fully 3D printed
• No hardware
• No supports
• Simple, functional, and easy to print

It still mounts directly on the back of the toilet tank, keeping the roll accessible without drilling holes or installing wall brackets.

Single and Double Roll Versions

I’ve included both single-roll and double-roll variants.
The double version is surprisingly handy — not just as a backup roll, but also if you like having different paper types available.

Both versions use the same compliant post idea, so they handle modern rolls equally well.

Print Settings

Functional designs (such as this one) generally require more strength than non-functional designs and more strength than the typical default slicer settings provide, so please review your slicer settings carefully.

This product was designed for a 0.4mm nozzle and a 0.2mm layer height. For best results, I suggest the following:

Assembly Notes

No assembly required.

Why This Update Matters

This is a good example of why I like iterative, real-world design. Nothing about toilet paper holders is glamorous — but when something that used to work suddenly doesn’t, the fix needs to be simple, reliable, and durable.

Gen 2 exists because the world changed slightly, and the design needed to adapt.

Try It Out

If you’ve noticed rolls slipping off older holders or not fitting the way they used to, this version should solve that problem cleanly. As always, feedback is welcome — especially if you run into edge cases or unusual roll sizes.

The post Toilet Paper Holder 2 first appeared on logicalplanet.