PURPOSE: To prevent the sharp lowering of friction torque, by forming an opening, having the effective diameter of a male screw, on a plate body, also forming notches toward outside from one edge of the opening, and dislocating the piece parts on both the notch sides each other to form the pitch of the male screw.

CONSTITUTION: An opening 2, having the effective diameter of a male screw, is provided on the plate body 1 such as synthetic-resin-made one, etc. Notdhes 3 are formed toward outward from one edge of the opening 2. A notch 3 is appropriately selected by the thickness and raw material of the plate body 1. One side, e.g. a piece part 4', out of piece parts 4 and 4' on both sides formed by the notch 3, is displaced to a spiral to form the pitch P of the male screw. That is, the piece part 4' is dislocated so that the lower end surface (b) of the piece part 4 and the upper end surface (c) of the other side piece part 4' ban be located on the same position, forming the male screw pitch P on between both the piece parts 4 and 4'.