Welcome to the forum. Here are a couple of links that might set you in the right direction.
Here is tutorial for them with pics:
http://www.briansmodelcars.com/tutorials/tutorial.asp?TutorialID=1&CurPage=1
How to make working door latches,might be a little more than you looking for though. They do have all sorts of great stuff on thier home page:
http://modeltech.tripod.com/geary_latch.htm
I also have some links on my site for auto buidling where you might find some useful stuff, Feel free to check them out.
http://www.lizardsworkshop.50megs.com/autolinks.html