- 1). Install the railings on the sides of the truck beds. These are the long rails which support the cover. In most cases these are clamped to the bed with clamps provided by the custom cover manufacturer.
- 2). Measure the length between the two rails at either end. The length should be exactly the same for the cover to fit. Check the documentation included with your custom build cover to know precisely how far apart the railings should be from each other. If one side is slightly off, move it back or forward until the railings are perfectly parallel throughout the entire distance. Tighten the railings down with the clamps provided.
- 3). Install the cover in the bed, behind the cab of the truck. The cover must be bolted to the railings using the bolts provided and a wrench. A retractable cover can be pulled across the bed to cover the entire surface. For a folding cover, follow the directions provided for folding and unfolding the cover.
Source...