The rearward section can be moved longitudinally to adjustably locate its rearward edge in {HEAD ~ a selected position} forward of {TAIL ~ the trailers} wheel assembly 
The rearward section can be moved longitudinally to adjustably locate its rearward edge in { HEAD ~ a selected position } forward of { TAIL ~ the trailers } wheel assembly
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH