The shutters may be resiliently deformable so as to deflect upon contacting {HEAD ~ such wall portions} to exert {TAIL ~ yieldable force thereon} 
to exert
The shutters may be resiliently deformable so as to deflect upon contacting { HEAD ~ such wall portions } to exert { TAIL ~ yieldable force thereon }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL