A method of bolting a strut mount to a curved outer tube mounting plate (6) without increasing the size of a bolt hole, comprising the steps of inserting the tube part (13) of a caulked nut (5) into the nut mounting hole (11) in the installation piece (10) of an outer tube (2) from the underside and caulking the periphery of the nut installation hole (11) to reduce the size thereof so as to fix the caulked nut (5) to the nut installation hole (11).
