To enable a user to assemble and disassemble the detachable front end section of a tool in a natural posture and make a joint between a base body and a front section transmit a large torque.

A joint including a male type portion (12) on the detachable front end portion and a groove (4) in the base body exists between the base body and the front end portion. Two offset leg portions (6) are regulated by a slot (5) to form a jaw portion for accommodating and tightening the male type portion (12) in the leg portion. A maximum width (W) of the jaw portion based on a bias of the leg portion (6) is larger than a maximum width (B) of a wedge portion (15) inclined in the male type portion. Besides, the respective inclined angles (α, β) of the side surface (18) of the male type portion and the side portion surface (25) in the groove are the same, thus securing a surface contact between these surfaces when each of the leg portion (6) is tightened to the male type portion.