The lettering guide is mounted upon {HEAD ~ the planar surface} for {TAIL ~ rectilinear movement} along a plurality of parallel steps 
for
The lettering guide is mounted upon { HEAD ~ the planar surface } for { TAIL ~ rectilinear movement } along a plurality of parallel steps
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH