For a large class of
closed orientable 3-manifolds, we define a new decomposition method which
uses embedded one-sided surfaces and is analogous to Heegaard splittings.
The technique is most useful for studying some “small” 3-manifolds (i.e.,
which have finite fundamental group or are not sufficiently large). We give
several general criteria for existence of these splittings and some results on
nonorientable surfaces in lens spaces. Also stable equivalence (as for Heegaard
splittings) and a result of Waldhausen’s are shown to carry over to the one-sided
case.