  We propose a string theory model which explains several features of two
dimensional YM theory. Folds are suppressed. This in turn leads to the empty
theory in flat target spaces. The Nambu-Goto action appears in the usual way.
The model naturally splits into two (chiral) sectors: orientation preserving
maps and orientation reversing maps. Moreover it has a straightforward
extension to 3 and 4 dimensional space-times, which could be the rigid string
with the self-intersection number at $\theta=\pi$.
