keel1 (def 6).
a table giving the lengths of the hypotenuses of right isosceles triangles of varying sizes: used especially for calculating the lengths of diagonal braces.
something that holds parts together or in place, as a clasp or clamp. anything that imparts rigidity or steadiness. Also called bitbrace, bitstock. Machinery. a device for holding and turning a bit for boring or drilling. Building Trades. a piece of timber, metal, etc., for supporting or positioning another piece or portion of a framework. […]
a triangular piece of wood used for propping up scenery from behind.