The upper inside surface and {TAIL ~ the lower inside surface} of the housing define a group of slots and a rear wall of the housing defines a plurality of {HEAD ~ openings} 
The upper inside surface and { TAIL ~ the lower inside surface } of the housing define a group of slots and a rear wall of the housing defines a plurality of { HEAD ~ openings }
OTH OTH OTH OTH OTH TAIL TAIL 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 HEAD HEAD HEAD HEAD HEAD