Capstone

n.

1.

(Paleon.) A fossil echinus of the genus Cannulus; - so called from its supposed resemblance to a cap.

Noun	1.	capstone - a final touch; a crowning achievement; a culmination Synonyms: copestone, finishing touch
	2.	capstone - a stone that forms the top of wall or building Synonyms: coping stone, copestone, stretcher

copestone, finishing touch, touch