How to Install UnderCover Flex Tonneau Cover on your F-150

Technical Note. UnderCover designed their Flex Tonneau Cover with a vehicle that does not have a plastic bed liner. If your F-150 is equipped with that type of bed liner, some minor trimming may be required. This instruction guide was created with the use of a F-150 with a plastic bed liner, but no trimming was needed.

1. Locate the included Side Rails, so they can be attached to the truck bed. The Side Rails are side specific and the drain tube fitting will go towards the front of the bed (near the cab).

2. Grab one of the Side Rails and position the top edge of the rail 1/8 in. above the top edge of the F-150 bed rail.

3. Using three (3) of the included six (6) clamps, attach the one of the Side Rails to the truck bed by positioning the clamps adjacent to the rail spacers. It would be best to start with the Middle Clamp.

a. If you are unable to position one of the clamps adjacent to the Rail Spacer, simply move the clamp forward or back.

4. Use a 1/2 in. Wrench or Socket and snug down the bolts on the clamps, do not over tighten the clamps, as this will give the ability to adjust the Side Rails if needed.

5. Repeat Steps 2-4 for the opposite Side Rail.

6. Locate the included Bulkhead Seal and attach it to the front rail of the truck bed, and then cut to length with the use of Scissors or a Knife.

a. Since the F-150 used in this installation guide featured a Plastic Bed Liner, the Bulkhead Seal was attached to an edge on the underside of the Tonneau Cover.

7. Locate the two (2) front mounting bolts and slide them into the track on the underside of the Tonneau Cover.

8. Place the Tonneau Cover onto the Side Rails with the smallest panel facing towards the front of the bed and the front flap covering the front rail.

9. Carefully unfold each panel and position it so it is centered from side to side and front to back on the truck bed.

10. Make sure the Rear Most Panel (towards the tailgate) closes smoothly with the latches engaging with the Side Rails. This will help to determine if the Tonneau Cover is centered.

a. If your vehicle is equipped with a tail gate protector, you may to raise the rear of the side rails slightly in ordered for the latches to engage properly.

11. Once the cover is centered, carefully fold the cover up to the open position by pulling the release cables on the Tonneau Cover to release the latches from the Side Rails.

a. In ordered to attach the Tonneau Cover Mounting Hardware easier, you may want to temporally lean the cover against the truck cab.

b. So you don’t scratch paint on the truck cab, grab a piece of the packing material from the box that your cover was shipped in and stick it between the cab and cover.

12. Once the cover is in the open position, go back and tighten the clamps that are attaching your Side Rails to the truck Bed. Do not over tighten the clamps, a torque wrench is not needed, if you want to use one, only tighten the bolts to approximate 75 inch lbs.

13. Locate the included Retainer Clamps, Flat Washers, Lock Washers and Star Knob.

14. Attach the hardware to the front mounting bolts that was previously inserted into the track on the underside of the Tonneau Cover back on Step 7.

a. Make sure the retainer clamp is clamping to the side of the Side Rail correctly.

15. Make sure the cover is closing properly and still centered before hand tighten the Star Knobs.

16. Locate the included two (2) Drain Tubes and attach them to the fitting that is at the front of the Side Rails.

17. Position the Drain Tubes to divert water out of the bed, whether it be behind the bed liner, through a factory hole or by drilling a 5/8 in. hole in the bulkhead.

18. Make sure everything is lined up and the Tonneau Cover is closing properly, then the installation of your new UnderCover Flex Tonneau Cover is complete.