Imagine a pair of socks, infinitely duplicated, each pair containing one left and one right sock. They're placed on a conveyor belt, which somehow magically appears to have a beginning and an end. The left sock of the first pair is placed on the left end of the conveyor belt. As the belt moves, a new left sock is placed on the right end. But wait, the new left sock is actually the right sock from the previous pair! This goes on forever, with the left sock from the current pair always being the right sock from the previous pair, and vice versa.