The load carrying capacity, stiffness, and strain fields of 18 mm thick and half lap 30 mm thick L-shaped furniture self-locking frame joints made of a Finnish birch plywood and a birch battenboard were determined. The joints were tested under tensile and compression bending. On the basis of the experimental information, finite element analysis models were verified. The data showed that the joints made of birch plywood reached a higher load carrying capacity and stiffness than the joints made of the birch battenboard with the same thickness. The Half lap joint (H L J) made of the Finnish plywood reached the ultimate load carrying capacity and the ultimate stiffness under both the compression bending and the tensile bending. The finite element analysis models of the joints can be used for estimating the mechanical properties of the self-locking joints with different tenon shapes made of the materials used in this paper.