A coupler for joining two objects comprises an insertion member attached fast to one of the objects and a reception member attached fast to the other object and used for admitting the insertion member into fast engagement therewith. The insertion member is provided with a setting portion for fast attachment to the aforementioned one object and a shaft extended from the setting portion and possessed of a radially expanded engaging portion at the leading end thereof. The reception member is provided with two generally semicylindrical shells connected to each other through a thin-walled hinge portion and adapted to form one cylindrical shape upon being closed onto each other along the matched edges thereof and a plurality of resilient engaging pieces regularly spaced in the longitudinal direction on the inner wall of each of the shells.