Retrax PowertraxPRO XR Electric Retractable Tonneau Cover with T-Slot Rails for 2019-2027 Chevrolet Silverado 1500 / GMC Sierra 1500 (5'8" Bed, without CarbonPro Bed)

Here's the short version. Follow Retrax's install sheet (below) for your truck's exact steps, part letters and torque settings.

1. Run the power harness. Wire-tie the fuse-holder end of the harness (red and brown wires) near the battery, but do not connect it to the battery yet. Route the harness to the driver side and down along the frame rails to the bed, as high as possible and clear of moving parts and the exhaust, with a wire tie every 2-3'. Bring it into the bed through the driver-side drain hole (wrapped in the split wire loom) or through the gap between the cab and the bed, leaving about 24" in the bed.
2. Assemble the cover. Remove the shipping screws, brackets and white shipping tubes from both sides, and keep one shipping bracket to use as a spacer later. Pull the cover 6-8" out of the canister and hold it there while you guide it into each side rail's channel and seat the rails in the canister. Fasten the rails to the canister with the four 10-32 x 7/16" screws, then slide the front cover under the rails and fasten it through the top of the rails with the two 10-24 x 3/4" screws and the 1/8" Allen wrench, all to 32 in-lb. Leave the protective film on until the end.
3. Set it on the bed. Some drop-in bed liners need notching at the front corners to clear the canister. With two people, lift the cover onto the bed with the canister at the bulkhead and the front seal lying flat on the bulkhead; trim the seal if it runs past the bed rail caps. Slide the cover back and use the shipping bracket as a spacer to set both rails 1/8" from the tailgate.
4. Clamp the rails. The T-slot rails use adjustable-back clamps built for the extra load: tuck each clamp's top jaw firmly into the top inside corner of the bed rail sheet metal, loosening the screws to reset the jaw if it does not seat, with both sets of teeth fully engaged. Fit the clamps between the adjustment screws front and back and tighten them with a 9/16" wrench while you push the rail down and tilt it up about two degrees, which Retrax says keeps water out best. At each clamp, slip a rubber shim between the truck's plastic bed cap and its metal bed rail, behind the adjustment screws.
5. Square the rails. Measure across the rails on top of the front cover and again above each clamp; all three must match within 1/16". If they don't, remove the clamps, turn both white adjustment screws with the 6mm Allen wrench (one full turn moves the rail 1/16") and re-clamp. With the cover closed and latched, the weatherstrip should show equally on both sides; if one side shows less, move that rail forward toward the cab. Once the rails are square, loosen each clamp's jam nut, run the stand-off bolt in until its bumper firmly contacts the bed wall and re-tighten the jam nut; Retrax says not to over-torque the bolt.
6. Drains, power and checks. Peel off the protective film and click a drain tube into each side of the canister (turn it clockwise until it clicks twice), routing the tubes out through the factory bed plug or another suitable hole. Plug the power harness into the electronics connector labeled "P", connect the red fused wire to the battery's positive post and the brown wire to the negative post, and fit a fuse in the fuse holder. Hold the fob button to open or close; one press lights the bed, and the light shuts off after 3-5 minutes. Check that the cover rolls without rubbing or binding and re-check the clamps after the first week of driving.