User manual CHAMBERLAIN 8808CB

[. . . ] The trolley must be in down (closed door) position during assembly and installation. If you have a completely installed garage door opener, the rail/opener assembly must be taken down. [. . . ] Be sure to keep it right side up: the idler pulley bolt hole above the window is larger on top of the rail than on the bottom. Slide the front rail onto the assembly; tabs along the side will lock into place. As a temporary stop, insert a screwdriver into the hole 10" (25 cm) from the front end of the rail (Figure 2). Grasp the end with the hooked trolley connector and pass approximately 12" (30 cm) of belt through the window. Keeping the ribbed side toward the rail, and allow it to hang while you complete the next two steps. Replace the 1/4"-20x1-3/4" bolt and lock nut into the trolley stop hole. Pull the belt around the idler pulley and hook the trolley connector into the retaining slot on the trolley (Figure 4). With the trolley against the pliers, dispense the remainder of the belt along the rail assembly toward the opener and around the sprocket. Check to make sure the belt is not twisted, then connect it to the flat end of the trolley threaded shaft with the master link (Figure 4): · Push pins of master link bar through holes in end of belt and trolley threaded shaft. Slide clip-on spring over cap and onto pin notches until both pins are securely locked in place. Hold the belt at the trolley shaft as you thread the spring nut by hand (Figure 5) onto the shaft until finger tight against the trolley. Insert a screwdriver tip into one of the nut ring slots and brace it firmly against the trolley, as shown. [. . . ] To avoid possible SERIOUS INJURY from a falling garage door opener, fasten it SECURELY to structural supports of the garage. Concrete anchors MUST be used if installing any brackets into masonry. [. . . ]