A boat is positioned between the mobile boat supports and {HEAD ~ the mobile boat supports} are moved inwardly on the deck to {TAIL ~ positions} adjacent the boat 
A boat is positioned between the mobile boat supports and { HEAD ~ the mobile boat supports } are moved inwardly on the deck to { TAIL ~ positions } adjacent the boat
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH