A surface or mass provided to withstand thrust, for example, the end supports of an arch or bridge. In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front abutment (the solid coal ahead of the face) and the back abutment (the settled packs behind the face).