How To Use JessEm's Box Joint Jig | Step-By-Step Instructions Our Box Joint Jig creates perfect joints in minutes! That's a ton of time saving on making table saw jigs or cutting these by hand! Here's a step-by-step guide on how to use your Box Joint Jig: 1. Choice between one of the three box joint sizes (1/4", 3/8" or 1/2") and install both the key and matching fence face onto the jig. Make sure the bit in your router matches the chosen key/fence size 2. Attach your jig to the base and set eve