Will Any Jack Do?

[75sierraclassic]

I've been without a jack in my truck since I bought it because it didn't come with one. I know some of your guys trucks didn't have one either, what are you using? Junkyards back home removed all of the jacks so that you couldn't jack anything yourself while you were in the yard, where can you get a used one at? Will a jack out of any car do? I would think that they didn't design a jack for each cars weight. Anybody know if load ratings differ between vehicles?