|Here is how Chris built
"I used 2" x 6" and lag bolted
the ends together, then levelled everything starting from the highest corner
using cut up pieces of angle iron driven in the ground, then screwed into
the 2" x 6" when level.( I found some steel shelving uprights with holes
already drilled). I have about a 12" difference from high corner to low
corner. The total size is 18' x 20'. I then filled the gaps below the 2"
x 6" with strips of 1/4" plywood screwed from the inside dropping down
to the ground where ever necessary in the low areas to support the tarp.
I then packed snow around the outside of everything for extra support."
Good job and thanks for the picture, Chris.