Abstract: An insert-holding seat is formed on a first part of a coupling device, defines a receiving hole, and is formed with an engaging groove. A limiting member is disposed rotatably and rearwardly of the seat, and has a tongue-arresting groove. An insert is formed on a second part of the coupling device, and has an engaging tongue that is disposed rearwardly of the seat when the insert is inserted into and through the receiving hole in the seat. The limiting member is rotatable relative to the seat from a first angular position, where the tongue-arresting groove in the limiting member is angularly offset from the engaging groove in the seat, and to a second angular position, where the tongue-arresting groove is registered with the engaging groove in the seat.