The thread of winter splits in two when the year comes to an end. One half symbolizes the year you were just in, and the other symbolizes the new year beginning, cutting winter in half and finishing off the year.
Right as winter ends you grab the two threads and lace them into your shoes (しゅう). Oh, you thought these were metaphorical? No they're real threads, although, they're technically shoe laces now.
Currently there are no similar looking kanji which exist in the WaniKani learning system