Custom End Cap Generator for Square/Rectangle Tube

About this generator

Custom End Cap Generator for Square/Rectangle Tube is a free MakerWorld customizer by SY3D that makes push-in caps for hollow steel or aluminum box tubing. Instead of hunting through a hardware store for a plastic plug that fits, you measure your tube and type four numbers into the Customize panel: outside width, outside height, wall thickness and the radius of the outer corners. A Fusion file does the modeling in the background, so you never open CAD yourself.

Width and height can each be set from 24 to 220 mm, which covers both square and rectangular profiles, and the wall can be 0.5 to 14 mm thick. The visible face of the cap matches the outside size you enter, while four springy legs about 40 mm long grip the inside walls. The creator says it prints face down without supports and that PETG gives more spring than PLA. Since February 2026 it has been customized close to 12,000 times.

It suits fence posts, stair rails, frames and furniture where an open tube end looks unfinished. The creator calls the caps decorative, because the legs flex against the layer lines, and the tube needs at least 40 mm of empty space inside. The Standard Digital File License covers personal use only.

What you can make

• Square tube end caps
• Rectangular tube end caps
• Press-in plugs for fence and railing posts

How to use Custom End Cap Generator for Square/Rectangle Tube

1. Measure the outside width and height of your tube
2. Measure the wall thickness and the outer corner radius
3. Open the model on MakerWorld, click Customize and enter the four values
4. Generate, download the file and print it face down without supports
5. Press the cap into the tube end