Moebius Scarf

Möbius Scarf by Cliff Stoll.

A Möbius strip is a one-sided, one-edged surface. You can make one by giving a strip of paper a half-twist, then taping the ends together. The scarf is knitted so that it forms a loop with one continuous surface.

See also "Immersed in Klein Bottles" and "Folding a Klein Bottle."