Device to identify bolts and nuts by size. SAE sizes from #4 up to 1/2, with customizable openscad file. There are ruler tic-marks along one edge for measuring bolt lengths. After printing you will need the following to populate it: (1) 3/4" x #4 machine screw and (2) #4 nuts. Ditto for #6, #8, #10. Then (1) nut and (1) bolt each for 1/4, 5/16, 3/8, 7/16, and 1/2. Glue in the bolts and nuts, taking care to put them in the proper columns as shown in the picture, because bolt head sizes occasionally differ from the sizes of their matching nuts. Bolts of the same diameter can come with different thread counts, so either pick the thread you use most for each size, or make 2 of these gizmos to cover both coarse and fine threads. You can also fill in the lettering and the ruler tics with caulk of a contrasting color to your plastic. I had more luck with this if I inverted my original print in the z direction so the 'lettered' surface printed smooth, making it easier to cleanly wipe off excess caulk.