Sentence:  ... if you deſign it a Fence to keep in Deer, at every eight or ten Foot diſtance, ſet a Poſt with a Mortice in it to ſtand a little ſloping over the ſide of the Bank about two Foot high; and into the Mortices put a Rail ... and no Deer will go over it, nor can they creep through it, as they do often, when a <WSD>Pale</WSD> tumbles down. 
Meaning of the word marked with <WSD> tags:  A wooden stake; a picket.