Okay... we have installed several windows (windshields, door glass, wing windows and the like) before...but this rear window is going to cause marriage counseling!! Cannot figure out why this thing will not go in. We already have had it pop out one way causing me to push it back through opening very briskly towards my husband, who in turn could not grab it time and it fell to floor but did not break! I don't think we will be so lucky next time. We have examined the opening and decided there were a few places in which it needed a little straightening and still this window refuses to go in like it should. We have compared the seal, the glass and the opening and everything matches. I am at a loss - maybe there is a technique that would work better than the way we are doing it? Some secret tool or something - I don't know. If anyone has anything to share please do and you may very well save a man from being pulverized by his wife! The truck we are working on is a 53 3 ton I forgot to add. Thanks so much.