This jig is based on a similar jig built by Norm Abram on his TV show, New Yankee Workshop. It slides along the fence and provides excellent support for tapering long pieces like table legs. It also taught me a thing or two about handling aluminum.
The jig is made of 3/4″ birch plywood with 1/8″ thick aluminum L-bars on both sides for added rigidity. The adjustment arm is piece of 1/2″ birch plywood.