I used this product called 3M VHB (Very High Bond) Dual Side Tape to attach the metal covers over my middle windows of my bus. It is used to bond siding onto trailers and windows into high rise buildings as well as attaching spoilers to cars by the manufactures. You can find it on Ebay pretty reasonably priced. Just make sure the surface is clean, I used a pure alcohol cleaner and I bonded metal to metal and I put a bead of VHT silicone on the weather side of the just to make sure it stays dry, I did it just in case. This stuff is tough, it has been on for 30,000 miles through rain and snow holding 16 gauge steel panels on a 40 foot uni-body Bus.