A first retractable member is provided so as to be freely retractable with respect to the first location hole of a turning member in a state where the first retractable member makes contact with a fitting portion. The first retractable member turns the turning member based on a contact force with the fitting portion corresponding to advance and retreat with respect to the first location hole. The first retractable member moves a fourth engagement portion as the turning member is turned so as to change an engagement position with a third engagement portion, and thereby makes a head unit swing with the engagement position of a first engagement portion and a second engagement portion serving as a fulcrum point so as to adjust the position of the head unit in the fitting portion.