Probably the most unique concrete form I've built; this mailbox was formed with thick gauge plastic that I sewed at the edges.

The four sided plastic form was lashed to a 2x4 frame and form spikes screwed to its frame.  This tensioned the fabric as well as twisted the top of the form about 50 degrees from its base.

I'm still trying to figure out why I decided to pour this directly underneath a tree branch.