PURPOSE: To constitute framework of woodwork of a king of a long-sized material, by a method wherein the first dowel slit is formed by penetrating through in a longitudinal direction and the second dowel slit having the same diameter with that of the first slit is formed at least in the one flank at equal intervals in the longitudinal direction.

CONSTITUTION: For example, four pieces of the first dowel slits penetrated through in a longitudinal direction of a main body of a long-sized material 1a for woodworking are formed. Then the second dowel slits 3 are formed on the flanks each at equal intervals in the longitudinal direction without penetrating through to the flank on the opposite side. A distance between the two first slits 2, 2 facing on each other is made equal to a space between the second slits 3, 3 which are formed in the flanks each and adjoining to each other. With this construction, it is eliminated that the title material is subject to restriction as a member constituting woodwork and a long-sized material for woodworking, which is of wide application can be obtained.