Sentence:  Full rerebraces enclosed the entire upper arm, with a hinge to allow them to be opened and straps and buckles to fasten them shut. Below the rerebrace was the elbow piece called a <WSD>couter</WSD>. The <WSD>couter</WSD> was small and conical, often shaped to a point, with a wing on the outer side as on the poleine, and with buckled straps to secure the arm harness snugly to the arm. 
Meaning of the word marked with <WSD> tags:  A piece of armor which covers the elbow.