I am building a torsion box using corrugated plastic panel, and I find that I need a little someting to add rigidity to the joints.
This thing acts as a 'cap' for each of the joints in such a torsion box. It can be used without glue, or you can actually glue it in place.
The .scad has some easy parameters so you can select the gap size, and various lengths of things. Similarly, you can decide whether you want to have a hole in the middle of the thing, or not.
This particular project was inspired by a project in my daughter's art class.
NOTE: test_corners.scad is just for display purposes. There is nothing printable there really. It shows how the connector can be used in a torsion box construction.
1) Edit the .scad file to fit the width of your material. Change the 'gap' parameter.
2) Print as many as you need, typically one per joint
3) Assemble your torsion box, and place one cap over each joint