Sentence:  The cleverly constructed <WSD>latch</WSD> which Clayton had made for the door had sprung as Kerchak passed out; nor could the apes find means of ingress through the heavily barred windows. 
Meaning of the word marked with <WSD> tags:  A fastening for a door that has a bar that fits into a notch or slot, and is lifted by a lever or string from either side.