Our Heavy-Duty Trak is an 'L'-shaped, anodized-aluminum extrusion that is extremely straight and great for heavy-use commercial applications. This Trak contains four T-slots that accommodate the head of a standard 1/4' (6mm) hex bolt. A 1/2' (13mm) recessed indentation runs along the top and front side of the Trak for easy application of a self-adhesive measuring tape (sold separately).