Hi Neil,

re:
> When I try it - I get a big hole in the side instead of a cut of a solid.

That will happen if you're doing a boolean on an object that isn't a solid. One solution is to make your object a solid first before attempting the boolean or another way is to use the Edit > Trim command to cut things up. The Trim command works on a surface level and you manually pick which areas to discard. Booleans automatically decide which pieces to discard based on what solid volume they are contained within but they aren't able to do that well when your objects are surfaces instead of solids.

So if you're working with surfaces usually Trim is preferred rather than booleans. Booleans on solids are kind of like a "batch mode" version of trim that automate some of the steps like discarding pieces and joining them.

- Michael