PURPOSE: To enable the easy connection of members by providing a fan-shaped grooves on each surface of members to be connected, inserting a similarly shaped shaft from the entrance of the groove, and connecting their joint surfaces together only by means of the members and the shaft.

CONSTITUTION: A fan-shaped groove is provided on each surface of members to be connected. Then the joint surfaces of the members are brought together, a shaft of a shape similar to that of the groove is inserted from the entrance of the groove, and their joint surfaces are connected together only by the members and the shaft. Any shapes of numerous shapes can be adopted as those of the members and the shaft. However, the outer width 4 must be wider than the inner width 5. In addition, it is possible to use any of metal, wood, concrete, glass, a resin product, rubber, etc., for the material.