This cutter is designed to make keys for locks after you decode them with a Lishi pick, but it can also be used to nibble cuts into standard brass keys while impressioning or originating a key by hand. The cutter has markings etched into the cutter head to gauge the depth of cut. This tool makes a clean V-shaped cut with a flat bottom so your pins or wafers seat nicely. Faster than filing, this tool has a series of lines on the head to help gauge your cutting depths. Compact design is 7-1/8 long x 2 wide. Here is a video of a guy using them.

/watch?v=6RAU00AKLCQ