Can you "flip" static objects?

[SpiritSharD]

Grid snap is on, but I changed the value to 0.1 to make it more accurate.

I don't have problems getting two pieces of the same type of wall to fit together, but as soon as I go for a corner (with using a corner piece), or try to add a doorway, or make a prison cell, I encounter issues. All to do with my inexperience of course, but I was hoping there would be a way to ease the process.