Abstract: An air supply means includes a frame providing a valve seat and defining a valve opening. A valve body is adjustably connected to the frame. A plurality of V-shaped fasteners are used to secure the frame in an air duct. Each fastener has a pair of angularly disposed legs receivable in a slot in the opposed top and bottom walls of the frame, the legs meeting at an apex which is positioned toward the entrance to the duct. To attach the frame to the duct, a punch-like member is used to strike the apex of the fastener to spread the legs thereof and drive them through the slots in the opposing walls of the frame and thence, into the walls of the duct.