Double-Lock DL15 is a structural panel that is mechanically seamed during installation. The panel is an integral interlocking system by design that installs in one direction from a given starting point. A double male starter panel is available (for a minimal set-up fee) and may be installed in the middle of a roof area to achieve an asymmetrical layout. DOUBLE-LOCK utilizes the traditional SMACNA standing seam “double-lock” plate.