Each carriage has a rearwardly projecting tongue, slidably received in {HEAD ~ a slot} formed in {TAIL ~ flange structure} on the port plate 
formed in
Each carriage has a rearwardly projecting tongue , slidably received in { HEAD ~ a slot } formed in { TAIL ~ flange structure } on the port plate
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH