since dynomat is like 10$ a square foot...you can get the same stuff but its designed for roof flashing, you can pick it up at most contractor building supply store. you can get a big ass roll that will do every inch of your truck x2 for like 40$

What I used is similar to those. It was some leftovers from a big rig shop. They use it on flatpanels to stop them from flexing and vibrating. It has aluminum backing and what looks like tar to makeŽem stick. Smells bad but the smell fades fast.