In the embodiment shown in FIGS 8A and 8B {HEAD ~ a button} 25 comparable to element 24 is fixedly connected to {TAIL ~ a flexible closed end sheath} 4 
is fixedly connected to
In the embodiment shown in FIGS 8A and 8B { HEAD ~ a button } 25 comparable to element 24 is fixedly connected to { TAIL ~ a flexible closed end sheath } 4
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH