A scarf joint is used to join lengths of plywood or lumber into longer pieces. The joint has to make a smooth transition between the sheets of plywood, and also increase the bonding area for greater gluing strength. Instead of the long bevel that is usually cut, the scarf that we developed is cut in a series of steps that are 10 times as wide as they are long, making a 1.2" long scarf in 4mm plywood. Not only is this joint very strong, but it has two advantages over a traditional tapered scarf; the edge is sturdier than the usual sharp edge, and the steps make the joint self-aligning. If you are interested in more information about cutting stepped scarfs, there's an article in the Spring 1997 ShopBot newsletter.