Each of the pair of {TAIL ~ sensor block members} is provided with {HEAD ~ an inner surface} having a vertically extending recess 
Each of the pair of { TAIL ~ sensor block members } is provided with { HEAD ~ an inner surface } having a vertically extending recess
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH