I am assuming that you are talking about Tie Rod ends.
If that's the case, then 2 of them will be right hand thread, and two of them will be left hand thread.
I'm pretty sure the right hand thread ones, are the outers, but in actual functionality, it won't make any difference if they are installed opposite.
Might screw up the wheel alignment guy in the beginning though, if he's familiar in which way he has to turn them.