each said lock rod has {HEAD ~ a rib portion} extending across {TAIL ~ the upper end} thereof for engagement with said blocking device 
extending across
each said lock rod has { HEAD ~ a rib portion } extending across { TAIL ~ the upper end } thereof for engagement with said blocking device
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH