  The reparametrization symmetries of Witten's vertex in ordinary or vacuum
string field theories can be used to extract useful information about classical
solutions of the equations of motion corresponding to D-branes. It follows,
that the vacuum string field theory in general has to be regularized. For the
regularization recently considered by Gaiotto et al., we show that the
identities we derive, are so constraining, that among all surface states they
uniquely select the simplest butterfly projector discovered numerically by
those authors. The reparametrization symmetries are also used to give a simple
proof that the butterfly states and their generalizations are indeed
projectors.
