1st and 2nd gen bed skirts are bolted on. Geronimo's were welded on when we filled the seams in - his bed has no seams for the skirts, taillight boxes, or the panels across the back of the bed - it has a custom roll pan grafted into the rear pans. And the side marker, front and rear, are "floating" - bolts welded to the pans / fenders and the markers install from the back.