need to know too

Me too! There don't appear to be snap points on the corners of the foundations and ceilings.

the way I do it is place a ceiling piece in the corner, you can snap it so the middle of the ceiling sits on the edge of the wall, then snap the pillar to the ceiling and run it to the ground, then remove the ceiling.

Oh, ^ that's a good idea! What I've been doing is using S+ pieces, which have corner snap points, next to the piece I want. Sometimes I can take the S+ piece away after, sometimes when I try that the pillar demolishes and I just have to find a clever way to hide the S+ ceiling/foundation.

if using s plus, just use the fence foundations. then they are pretty much hidden once wall is placed