This template is sort of like a mini speed square for woodworking that you can keep in your apron pocket. I find it handy for marking out frames and borders as well as miters.

Diamond holes around the perpendicular slot are 5mm +/- 2mm, 10mm +/- 2mm, etc. For example to mark a 3mm parallel to an edge use the first diamond corner closest to the fence.

Suggest printing in PLA.

Hope this proves as useful for you too.