This invention relates to a coupling device that is easy to assemble, and just as easy to disassemble. This internal connecter device is shown here, as an example in the form of a rail. However it is not exclusively concerned with the formation of a rail. The xe2x80x9cclock lockxe2x80x9d can also be turned into the formation of a xe2x80x9cTxe2x80x9d-JUNCTION. Although its basic principles of operation do not change. With this method of assembly it is possible to achieve very flat external surfaces, at the point of connection, between two separate rails.
A system for joining two rails includes a rotatable disc in a slot in an end of a rail, where the disc has a pair of diametrically opposed notches, a pair of diametrically opposed first sectors having a first radius, and a pair of diametrically opposed second sectors having a second radius larger than the first radius. A movable stopper in the rail is urged into the slot at a position where the stopper engages one of the first sectors when a pin in the rail engages one of the notches, and one of the second sectors is between the one first sector and the notch engaging the pin.