A ladder support bracket has a support shoulder for creating a support contact with a complementary backup. The bracket includes at least one jaw for joining the bracket to an upstanding rail of a ladder, the jaw having also a retainer mechanism by means of which the bracket—when being attached to a rail of a ladder—can be brought into a clamping position attaching the bracket unmovably to the rail and a release position holding the bracket in a swivel connection relative to the rail and/or movably along at least a section of such rail.