What is the function of the side rail flange?

The side rail flange increases the stiffness of the rail and helps resist bending, twisting, and local deformation. It can also create a safer cable-contact edge, provide a seating area for covers, and help align couplers or fittings. In some product data, the flange dimension is listed as a key structural characteristic, which shows that flange height is not decorative but part of the mechanical design.