If you add an extension tray to your WM40 set, you’ll need to secure your WM40/TRAY to the underside of the table with an additional fastener bracket. Also sold individually for added support for heavier applications where large amounts of cabling are stored in the tray compartment. Or as replacements if needed. Fasten bracket to underside of table and clips to the front edge of the tray. By pressing the tabs on the clips, the WM40/TRAY will drop down to access cabling inside the trough.