When inspecting the coupling system on a combination vehicle, what is checked at the fifth wheel?

The fifth wheel inspection covers: (1) Mounting — bolts tight, brackets not cracked or bent, mounting bracket plates intact; (2) Locking jaws — closed around the kingpin shank, not the kingpin head, no visible space between upper and lower fifth wheel; (3) Release arm — properly seated and safety latch in place; (4) Skid plate — adequately greased, no excessive wear; (5) Kingpin engagement — fully seated in the throat, no high hitch; (6) Clearance — adequate space between the tractor frame and the front of the trailer so they will not contact during turns. Defects in any of these can lead to trailer separation while driving, one of the most catastrophic possible failures.