a stiffener defining an opening in {TAIL ~ a central portion} thereof and having {HEAD ~ front and rear ends}, the stiffener having an locking hook close to the front end along a first side of the stiffener 
a stiffener defining an opening in { TAIL ~ a central portion } thereof and having { HEAD ~ front and rear ends } , the stiffener having an locking hook close to the front end along a first side of the stiffener
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH