Abstract: A pair of elongated stabilizing supports and a pair of mounts for support by opposite side rails of the ladder. The stabilizing supports each include a pair of generally parallel arms and have a first pair of end portions free of connections extending therebetween and connecting structure extending between and connecting the second pair of end portions thereof. Support structure mounts the stabilizing supports from the mounts in upwardly convergent positions with the first pair of end portions uppermost and for lengthwise adjustable shifting of the stabilizing supports relative to the mounts. The first pair of end portions of the stabilizing supports, when the latter are in upper adjusted positions thereof, embracingly receive the corresponding ladder side rails therebetween.