Counterbrace

To counterbrace the yards is to brace the head yards one way and the after yards another.

Here a, b, and c are the great ribs whose thrusts, in the direction of the arrows, are concentrated upon the pier, d, and are counterbraced by the flying buttress, e. In other words, the section through the vaulting conoid at half its vertical height gives the triangle, a, b, c, in A, and not the square, a, b, c, d, in B in the same figure.