A big windstorm blew off several post caps from my outside decking. Some were lost, others were damaged, basically I was short 6 post caps at $12/cap. I spent a little time in F360 to come up with this replacement cap. This is designed to snuggly fit over a 4x4 composite sleeve. I added a hole at the top to secure the cap to the post. With a tight fit this may not be necessary.

The Sunlu roasted chestnut PETG was a great color match to the remaining caps. The photo shows the first print and with four horizontal perimeters and 10% infill you still see the infill pattern. Subsequent prints will increase horizonal perimeters. 

I printed with .3mm layers and I only needed support inside the cap extending up to the center hole. I was quite generous on the design wall thickness as I want this to last. I added a brim to make sure the print didn't detach. I included my prusa slicer file. I did not add any clearance tolerance to the plug. Tolerance could be added to "Top View" sketch or simply scale the plugs using the slicer.

I included the F360 file. You can change the profile sketch if you want a different profile. The entire cap and plug could be easily scaled to fit over a bare 4x4 post without sleeve.

4/27/2026 Added stls for base and three sided base.

For angled railing clips, see