The failure surfaces in the Douglas-fir 2-ply lap joint test samples were wholly within the grain of the wood up to the 4-inch glueline length; for longer glueline lengths, the breaks were increasingly in direct tension across the grain. A similar pattern was found for the birch 2-ply lap joint test samples, except that wood failure values increased from a base of about 30 percent for the 1-inch glueline length and the failure surfaces with longer glueline lengths occurred increasingly in the wood and in direct tension across the grain.