- anchor, mainstay, keystone, backbone, linchpin, lynchpin - a central cohesive source of support and stability; "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
--1 is a kind of support
- keystone, key, headstone - the central building block at the top of an arch or vault
--2 is a kind of building block
--2 is a part of arch
--2 has particulars: quoin, coign, coigne