PURPOSE: To obtain said jig without any machining by laminating reinforced plastics and fitting the hard parts into the hole from which the standard pin and the dummy parts are detachable after the separable dummy parts are inserted to the reference pin protruding from the original mold.

CONSTITUTION: The reference pin 6 is inserted into the master 4, the upper dummy bush 17 and the lower dummy bush 18 are inserted by guiding of the pin 6 and the jig body 1 is formed by laminating FRP material. Each other diameter of the bushes 17, 18 is made larger in consideration of the shrinkage due to the hardening of FRP material. After FRP material is hardened, the pin 6 is detached from the master 4, the jig body 1 is separated and the dummy bushes 17, 18 are detached, then the bush hole 8 is formed.