Tru Trac Rollers and roller guards were manufactured specifically for the fence industry. The rollers themselves are made of a type of plastic called UHMW. Unlike the typical cast roller the UHMW roller is mounted on a stainless steel shaft, with sealed greaseless bearings, mounted on a high grade aluminum alloy bracket. The bracket is held in place by 2 each ½" U bolts and mounted on a 4" o.d. gate post. As you can see in the attached drawing the 4 gates rollers are mounted on 2, 4" o.d. gateposts set in the fence line. Once the posts are set and the concrete is allowed to cure. The rollers are then bolted to the posts and that allows the gate to set in the rollers and will allow it to slide. After the gate is in place and adjusted properly the roller guards are installed on the top rollers. Please note the roller guards are manufactured by Guidance Systems. The guard is made by an injected mold process, that makes a hard durable cover that conforms to the shape of the roller and covers all the moving parts of the top rollers. The guards were designed to snap over the 1 ½" stainless axle and secured into place over the bracket with a 9 gauge tie wire. Again these covers were designed with the utmost safety in mind as well as easy installation. Also keep in mind these roller-guard covers are designed to retro fit any full cantilever roller foreign or domestic manufacturer.