An open string looks like a short line , so its worldsheet will look like a strip or , more generally , a PERSON@1 surface with a boundary .

A closed string looks like a small loop , so its worldsheet will look like a pipe or , more generally , a Riemann surface -LRB- a two-dimensional oriented manifold -RRB- with no boundaries -LRB- i.e. no edge -RRB- . An open string doing the same thing will have its worldsheet looking like a ring connected to two strips .
