I have been reading the Shapeways on how to ensure that your models are manifold before printing. I have two questions
- Water tight and manifold are two different things right?
(I ask this because http://www.shapeways.com/tutorials/fixing-non-manifold-models says not being water tight is a type of non manifold error)
- When you go to Edit Mode, and press ctrl-alt-shift-M what are you doing exactly?