Three or 4 bolts each side onto box section rails, but for some reason had to (in instructions) pull bumper and buffer/damper set by removing 2 large (maybe 14mm x 140mm approx) vertical bolts through rails from boot. Not sure why the bumper and buffers had to come out, unless it was to place a bar with tapped holes to receive the bolts through the rails. Know that it was a bit of a hassle to get the bumper to line up properly under the seal strips when replacing, used a trolley jack to support in the end I think. Hope it goes well