First pivot mount 40 and {TAIL ~ second pivot mount} 41 are formed on {HEAD ~ an upper surface} 50 of the support beam 31 
First pivot mount 40 and { TAIL ~ second pivot mount } 41 are formed on { HEAD ~ an upper surface } 50 of the support beam 31
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH