{HEAD ~ The convenient and easy use} of the machine is facilitated by {TAIL ~ the fact} that it includes a cavity or tunnel which is essentially vertical with a trap door or gate at the bottom 
is facilitated by
{ HEAD ~ The convenient and easy use } of the machine is facilitated by { TAIL ~ the fact } that it includes a cavity or tunnel which is essentially vertical with a trap door or gate at the bottom
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH