From BlenderWiki
Potential Features
Sculpting
Symmetrize + Masking
From Jason van Gumster:
"I've built this sculpt from a base mesh... that base mesh had asymmetry introduced to it pretty early on. I was under the impression that I could use the symmetry options where I needed them and turn them off when not needed. For the most part, this was true, but there ended up being some corner cases that turned out pretty ugly. In order to fix this, I was interested in masking off the parts I'd like to keep (see attached screenshot), such as the head, tail, and feet, but symmetrize the wings to give me a better starting point for tweaking on the mirrored side."
