PURPOSE: To surely turn a tightening shaft with this shaft unable to rotate in a grip handle by removably inserting the tightening shaft into the grip handle and forming the central part in a lengthwise direction of the tightening shaft into a non-circular section.

CONSTITUTION: A central part in the lengthwise direction of a tightening shaft 1 is formed into a non-circular section, many uniform hollows 11 are arranged with a space in the lengthwise direction on surfaces of the shaft 1 and a protrusion 31, which can be protruded and retracted toward the tightening shaft 1, is provided in a grip handle 2. This protrusion 31 is fitted to any one of the hollows 11 with the tightening shaft 1 fixed to the grip handle 2, and the tightening shaft 1 is turned by rotation-operating this grip handle 2.