I find that a pair of poles are very handy for climbing over stiles.  We have a lot of stiles in the UK, I'm not sure if they are a feature in US trekking.  They are also good for controlling the speed of your descent when coming downhill and they reduce the jarring on your knees.  I'm told that you should always use a pair of poles so that you don't twist as you walk, the only exception is if you have one damaged knee then you would use one pole for support.

[Wikipedia article about stiles][1]


  [1]: http://en.wikipedia.org/wiki/Stile