A drunkard crosses thread across special spikes to separate the fibers. The best way to separate the fibers of thread is to get a drunkard to do it. If you're too precise it will just snap. You gotta be loose with it! Just flop them onto the spikes and the fibers will come apart by themselves!
You stare at the fibers easily coming apart when you realize that this drunkard seems to have a few extra legs... and hair and a tail? This isn't just a drunk guy, it's a centaur (せん). Maybe separating fibers is really a centaur trick, and that's why normal people can't do it...
Currently there are no similar looking kanji which exist in the WaniKani learning system