The insert, when rotated with respect to a marking device, provides {HEAD ~ a relatively easy means} for varying the width of {TAIL ~ a stripe} 
The insert , when rotated with respect to a marking device , provides { HEAD ~ a relatively easy means } for varying the width of { TAIL ~ a stripe }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL