There’s a new option (2006 and up, I think) in the Hatch command called “create separate hatches.” While it has the potential to be a wonderful tool, it can be really annoying as well. For example, it’s great for columns, but terrible if you have grid lines crossing walls, or rebar forming closed loops in concrete. If you’re not careful, you could end up with a wall hatched with a hundred different pieces – imagine trying to edit that! If you are going to use this option, be sure that you turn off ALL extraneous geometry, i.e. everything that is not necessary for defining the hatch boundary. You need to do this because with this option, every point or object you pick becomes the boundary of a separate hatch. To be on the safe side, turn off everything you don’t need, and turn it on again after you hatch.