If someone falls overboard while you're white water rafting, you can use a long piece of thread as a life line. Sure it might be thin, but a line of thread is better than nothing. Throw them a line and drag them back aboard! Those white water rapids are vicious.
The person who threw you that line of thread is actually a centaur (せん). How kind of him. After you are safe you hop on the centaur's back and ride around to get the wind to dry you off.
Currently there are no similar looking kanji which exist in the WaniKani learning system