Then using 4" screws we attached the wheels to the bottom pallet.
Next, we took a 4x4 and used a miter saw to cut four 15" pieces. Then attached the 4x4 piece to each corner of the pallet by screwing at a down angle from the side of the 4x4 into the top of the pallet. We used the inside of the 4x4s to have less screws showing.
Finally, we put the other pallet on the top and screwed through the bottom board of the top pallet into the 4x4 corners.
and viola!
We are thinking of painting it black but have gotten lots of suggestions to stain it instead.