Box Joint Jig
Unlike most box joint jigs that require an almost endless amount of "tweaking," this jig can be set up in a matter of minutes. The secret is a built-in system that lets you adjust the jig in extremely small increments. The system is designed to adjust both the size and spacing of the pins and slots that make up a box joint. By simply turning a knob, the jig can be set to cut slots that range in size from a width of 1/4″ to 13/16″.
With the exception of the 1/4″-thick hardboard backing plate (that prevents chipout), all the main parts are made from 1/4″ or 3/4″-thick hardwood. The hardware is available at hardware stores and home centers.
Overall dimensions: 4" wide x 19-1/4" long x 6-1/4" high
Source: This project appeared in ShopNotes Magazine No. 8.