My 2012 Platinum has a roll n Lock tonneau cover the original owner had installed when they first purchased the truck. It works great but won't stay shut. I need to loosen the bed rail cover on one side and move it back so the cover will come back all the way and latch. The under-bed rail locking blocks are aluminum and the tightening screws are steel cap screws. Basically 2 dis-similar metals and they are frozen solid. I can't get the cap screws to loosen even after soaking twice with WD40. Does anyone have any suggestions on what lubricant might work? I'm really tired of filling the truck with heavy dust every time I go down a dirt road. Also, I know the latch slides into the side rail, but it looks like it's supposed to latch on a roller pin in the tailgate cap. Is this correct? TIA

 

PB Blaster would be better for rust. Not sure if it would help in this situation.