Rusty bolts/nuts? Tight slip fit parts? Ball hitch couplers? Even the screws in your taillight covers and that hold the taillights on. Do yourself a huge favor and spring for a jar of this stuff:

This stuff has several manufacturers, and is available most anywhere. I'm not pushing the twilight zone or the leprechauns but here's a couple links:
http://www.autozone.com/miscellaneous-cleaners-and-degreasers/lube/permatex-8-oz-226-8-g-anti-seize-lubricant/178722_0_0
http://www.oreillyauto.com/site/c/detail/PER0/80078/N0490.oap?ck=Search_N0490_1124828_494&pt=N0490&ppt=C0139
Also formulated with copper instead of aluminum. Either one is amazing in its longevity and effectiveness. I just pulled a water pump off of an old John Deere that had 12-69 scratched into it by my dad when he put it on. (He always marked parts that way when he'd replace something. I've picked up that habit too, it's kinda neat to know the trivia of how long something lasted

So, bottom line is, if you want to make it easy on yourself or your kids on down the line, pick up a jar of this stuff and use it every time you put a fastener together under your trailer!
