Instead of measuring for all the screws in a subwoofer box I decide to make a simple jig that has multiple holes set at a .500inch between centers. Now I simply measure for the first hole then make a second measurement to align the tool. Once the tool is aligned you can drill aligned holes by simply moving a given number of holes. Rinse and repeat for each new row/column of screws you want to install.

Designed for a 3/32" drill bit, used to pre-drill a hole for a #6 wood screw.