Abstract: A first support member having a web with a slot therein and a second support member having a web provided with an integral locking connector extending axially therefrom for insertion in the slot. The connector has a snap locking finger provided with an edge inclined relative to a true vertical for positive locking engagement against one side of the first support member web. Interlocking means are provided on the opposed faces of a pair of second support member connectors inserted through the slot for locking the second support members against axial separation.