I printed and tried many beautiful and over complicated 3d models and jigs to make perfectly vertical holes with the drill but none satisfied me. I made this super simple guide and have been using it ever since when I can't use my drill press. I glued a small L-shaped aluminum profile to reduce wear, i recommend you to do the same and use a little lubricating oil to preserve drill bits and jig. I use this guide for precision work on guitars with very small drill bits from 1 to 4 mm. If you need to use bigger drill bits you can scale the model 2x 3x and so on.