This is a centering jig for 10 mm barrel hinges to achieve a good alignment between the top and bottom half of a box. It will mark the opposite side using a brad nail located in the center. I used these 10 mm barrel hinges: https://amzn.to/2WIsXTG and a Fisch 10 mm Brad Point bit to drill the holes https://amzn.to/2Bj4GdF
Print as many as needed for placing the hinges you need. Insert a brad nail through the center hole and place the jig (nail-side-up) into the pre-drilled 10 mm bottom half hole. Place your lid with the alignment desired and press down to mark precise locations as to where to drill top half holes.