My driver side rear door (suicide door on quad cab) got difficult to open/shut, then I COULDN'T get it to open. The top latch would release but the bottom latch was frozen shut. I took the interior trim apart, took the handle assembly off, googled the problem (there were quite a few others with the same one), and followed the advice of one. Spraying rust-penetrating lubricant on the assembly within the door, between the door and frame (around where the latch was), and kicking it from the inside (while the other latch was relased). I did this several times over several months before I was finally successful in getting the darn thing to let loose. Then removed the bottom door latch (need a 13/32 socket) and will replace it eventually. Put everything back together and the door shuts (mostly) securely. Another inferior part problem. Why use something that will rust as part of a moving mechanism?