Adjustable Box Joint Jig
Each time I build a project that requires box (finger) joints I scab together a quick jig and have at it. I guess I have been lucky as it works out most of the time however I found out that sometimes you just have to be accurate especially with wide panels.
My last project required a box joint on 12 ¾ “sides. My test pieces worked out fine so I went ahead and cut the work-pieces. Unfortunately my test pieces were only about 3 ½ “wide. When I fit the 12” boards they started out great but by the end they were out and did not line up. The moral of this story is jig accuracy is vital over a long span.