Abstract: A pair of ladder brackets held together by an elastic tie at one end of each having U-shaped clamps at the other ends for engaging the narrow sides of the side rails of a ladder when the brackets are fitted to the outer wide sides of the side rails. The elastic tie holds the U-shaped clamps against the inner wide sides of the rails. The brackets can be slid along the rails without interference from the rungs. The free ends of the brackets engage the roof of a building against which the ladder leans, to prevent the ladder from being displaced sideways. The brackets can be carried in a small package up a ladder by a user, and installed while the user is standing on the ladder.