SAP
, or Sapp, in Building, as to sap a wall, &c, is to dig out the ground from beneath it, so as to bring it down all at once for want of support.
Sap, in the Military Art, denotes a work carried on under cover of gabions and fascines on the flank, and mantlets or stuffed gabions on the front, to gain the descent of a ditch, or the like.
It is performed by digging a deep trench, descending by steps from top to bottom, under a corridor, carrying it as far as the bottom of the ditch, when that is dry; or as far as the surface of the water, when wet.
