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.It should be noted that in all cases, the tension perpendicular values of the 2-ply samples were substantially lower than the published values for the solid wood (16) (Table 6).