Trying to remove step-rails on 2005 Explorer XLT. 13 mm nuts are off, but when I start to back-out the 13 mm bolts (above the nuts...closer to the cabin) bolts spin endlessly without dropping out. As if hidden nut or threaded plate is spinning. lifted carpet to attack from above...no luck. How do I now get these 13 mm bolts out of the frame so step-rail can be removed? Thank you.