I designed this to help hold up objects for spray painting. The included STL is 195mm long, with sides of 10mm, but it is also customizable for different lengths.

The rod includes a protrusion at one end and a matching void at the other, so multiple rods can be stuck together.

This is not intended to be a high-stress part, although with sufficient infill/walls, larger sides, and not trying to stretch the length too long, it could probably be reasonably strong.