keystone Synonyms

anchor headstone lynchpin key linchpin backbone mainstay vault trapezium tombstone vaulting support samara rule root quoin principle primum mobile voussoir wedge bedrock vital element main ingredient core element key element key note screw key ground rule foundation stone Keys coign ground tackle cornerstone building block screw wrench key fruit pivot ogive crux crown cotter core copestone concameration columella clef center calotte basis base