{HEAD ~ The covering} is stored on a reel, and pulled off from the reel as it is replaced, and {TAIL ~ the used covering} is taken up on a second reel 
{ HEAD ~ The covering } is stored on a reel , and pulled off from the reel as it is replaced , and { TAIL ~ the used covering } is taken up on a second reel
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH