If this method of superposition is not possible, locate by measurement.

Mark, with a knife point, on X, the thickness thus obtained.

Square both these lines as far across the edges of X as Y is to be inserted.

Gage to the required depth on both edges with the marking-gage.
To cut the joint: First make with the knife a triangular groove on the waste side of each line, as indicated in Fig.

91, p.