Hiking poles come in handy for a lot of things -- crossing rivers, probing mud depth, moving wet brush out of the way, and so on. Some people swear by them for helping support and balance the weight of a heavy pack, and they're an invaluable aid if you happen to fall while snowshoeing. But those same poles become a burden when you're not using them.
If you're carrying old ski poles, or any type of trekking pole that doesn't collapse down into a manageable bundle, you're pretty much stuck toting them around in your hands for the rest of the hike. But if your hiking poles are the collapsible kind -- if they telescope down to a manageable length -- you can stow them on or in your backpack, leaving your hands free for the rest of the hike.
Most backpacks have specific attachment points for holding trekking poles. The end result almost always looks like what you see in the picture. Click "Next" to see how to attach your hiking poles to your backpack the conventional way, plus a few alternative arrangements in case your pack doesn't have the right attachment points.