1.  capstone(n = noun.cognition) copestone, finishing touch - a final touch; a crowning achievement; a culmination;
is a kind of touch

2.  capstone(n = noun.artifact) copestone, coping stone, stretcher - a stone that forms the top of wall or building;
is a kind of stone
is a part of wall

   A fossil echinus of the genus Cannulus; -- so called from its supposed resemblance to a cap. [1913 Webster]

capstone, n. coping; a coping-stone.