Adjustable Box Joint Jig
Although most box joint jigs are single-use items, the shop-built adjustable box joint jig in Ralph's article from the 2004 Winter Collector's Edition of Woodworker's Journal has the distinct advantage of being reusable.
Use just one jig to make all of your box joints. The indexing key adjusts side to side for different fingers and a replaceable backer prevents tearout. Published in Woodworker's Journal, Feb 2002.
Adjustable Box Joint Jig Article, Woodworker's Journal, Winter 2004 Collector's Edition