PURPOSE: To simplify attachment and prevent corrosion due to contact with metal members by providing a plastic shank, comprising a cup-like base for receiving a washer with claws and an elastic deformable blade portion.

CONSTITUTION: First, a washer 2 for a fastening member is integrated with a shaft 1 by a rib 6 of a blade portion 5, so that the washer cannot escape from a cup 4 on a base 3. Secondly, the shaft 1 is inserted into an orifice O on a wall P, and the blade portion 5 is deformed in the direction of the diameter until an outer groove 8 of the blade portion 5 is clamped onto the orifice O. A pin T of a shield E is pressed via the washer 2 and claws 10 of the washer 2 are hooked onto the pin T, so that it is firmly attached on a wall E without possibility of coming off the claws 10 of the washer 2. Therefore, it is possible to mount the pin T on the shield E on the wall P from one side and at the same time dispose a fastening member at a place away from the wall P using the washer 2. Moreover, when the method is applied to vehicles, the method can solve the problem of corrosion due to attachment.