appui

(transitive, military) To prop or support, e.g. by posting troops.

(obsolete) A support or supporter; a stay; a prop.

(horse-riding, obsolete) The mutual bearing or support of the hand of the rider and the mouth of the horse through the bit and bridle.

Clipping of point d'appui. [(military) A given point or body upon which troops are formed, or by which they are marched in line or column.]