Pull your trekking poles apart and let everything dry following a particularly rainy hike. Performing this simple maintenance will help to prevent the barrel adjustment screw from corroding like the one in this photo.
Once the screw corrodes, the barrel adjuster freezes and your poles neither expand nor collapse. Some newer poles appear immune to this problem, but it never hurts to be on the safe side.
If you don’t feel like completely dismantling your poles, at least expand them and give everything a quick wipe down before putting them away. Doing this, even with new poles, also affords the opportunity to visually inspect your sticks to ensure they’re in good working order for your next hike.
See you on the trail!