A retaining wall is a structure designed and constructed to resist the lateral pressure of soil; when there is a desired change in ground elevation that exceeds the angle of repose of the soil. a basement wall is thus one kind of retaining wall. but the term usually refers to a cantilever retaining wall; which is a freestanding structure without lateral support at its top. these are cantilevered from a footing and rise above the grade on one side to retain a higher level grade on the opposite side. the walls must resist the lateral pressures generated by loose soils or; in some cases; water pressures.