This double finger miter or double finger butt joint with an added lip is excellent for conservation because the mortise is partly closed by the added strength for the joint, and because tacks can be put closer to the corner without causing splitting. It is also possible to make an out-of-square stretcher with the miter meeting at the corner. Lips are added on with a wooden biscuit (plate) joiner.

Bar Profile: L Shape Biscuit Joint