Means are provided for mounting {HEAD ~ the slotted member} upon {TAIL ~ the substrate} and permitting the rectilinear movement thereof in a plurality of parallel spaced steps 
upon
Means are provided for mounting { HEAD ~ the slotted member } upon { TAIL ~ the substrate } and permitting the rectilinear movement thereof in a plurality of parallel spaced steps
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 OTH OTH OTH OTH OTH OTH OTH