A pair, a couple; originally used of dogs, and later of animals generally (e.g., a brace of conies) and then other things, but rarely human persons. (The plural in this sense is unchanged.) In British use (as plural), this is a particularly common reference to game birds.
A piece of material used to transmit, or change the direction of, weight or pressure; any one of the pieces, in a frame or truss, which divide the structure into triangular parts. It may act as a tie, or as a strut, and serves to prevent distortion of the structure, and transverse strains in its members. A boiler brace is a diagonal stay, connecting the head with the shell.