I was making a small enclosure out of acrylic and needed some right-angle brackets to hold the thing together. It turned out to be as easy to design these in OpenSCAD as to find somebody else's design that would do the job for me. The .scad file has parameters giving choices for the basic dimensions - length, width, thickness, bolt-hole size. There is a parameter to choose whether to have the bolt-holes aligned with each other, or staggered to stop bolts clashing. Version 2 of the .scad file includes an option to print a half-width bracket, with just one bolt hole. The .stl files are the dimensions I used for my project. My brackets were printed in PLA and do the job fine.