BONDSTONE

Etymology

Noun

bondstone (plural bondstones)

A stone for bonding masonry to a similar backing; a stone that reaches a considerable distance into, or entirely through a wall, for the purpose of binding it together.

Source: Wiktionary

Bond"stone`, n. Etym: [Bond,n.+ stone.] (Masonry)

Definition: A stone running through a wall from one face to another, to bind it together; a binding stone.

Source: Webster’s Unabridged Dictionary 1913 Edition