A safety device loosely extends from the first channel to the second channel when {HEAD ~ the first and second channel} are disposed in {TAIL ~ the first operative position} 
A safety device loosely extends from the first channel to the second channel when { HEAD ~ the first and second channel } are disposed in { TAIL ~ the first operative position }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL