Here is how it mounts.
The L-brackets they provide slide inside of the rear framrails. They have two 1/2" bolts that go into the sides of the frame rails through existing holes, on each side. Plus, you re-use the additional two holes on the sides that the stock bumper bolts into. They have welded nuts on the L-bracket inserts (two on the side, one on the bottom). That last bolts goes into the L-bracket on teh bottom of the frame rail.
BUT..........There was NO EXISTING HOLE on the passenger side of the framerail! (there was on the driver's sdie). I had to drill it out myself on the PS. You need to make a 1/2" hole.
Note the bottom of the frame rail. You put a bolt through that first one on the bottom. But, again, there is only a hole on the DS.
L-Bracket goes into frame rail.