Consider packing some metal cup hooks, especially if you are backpacking.
I am talking about the small, light, metal cup hooks that screw into wood. I prefer the ones that are thin and have a white or black paint or thin plastic coating as I think they will resist rust better than the 100% metal ones. They come in packs of five or so.
Why I recommend packing some cup hooks for your travel.
As a backpacker, I keep wishing I had a hook upon which to hang my towel or a garment. Hostels don’t have closets with hangers.
REI, Sea To Summitt sell lightweight clothing lines that can be very helpful but you still need places from which to hang the line. My REI clothing line has clips, suction cups, and Velcro bands — but I am still typically unable to find away to hang it. Many hostels have wooden porches (or bunks) and if they only had a nail in two well-spaces beams I would be able to stretch that line. However, that nails are not there. I would love to be able to screw in a cup hook to use while there and perhaps leave for the next people.
I have also stayed with people in places where such hooks are not readily available and the gift of leaving a few behind would have been nice.