The cam plates are in {HEAD ~ contact} with {TAIL ~ the cam surfaces}, and serve for positioning the sliding frames 
with
The cam plates are in { HEAD ~ contact } with { TAIL ~ the cam surfaces } , and serve for positioning the sliding frames
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH