Abstract: A brace for use with a step ladder has a platform that resists shear forces and two runners. The runners are one located opposed sides of the platform and configured to fit over the unfolded struts of a step ladder. In use, a brace as described above is placed with its runners fitting over, and resting on, the struts of a step ladder. The brace stabilizes the ladder, helps prevent injury to the struts if the ladder falls over and may also force distorted struts into a better alignment. Optionally, the platform may also provide one or more surfaces for supporting tools, for example by way of a sliding shelf. Optionally, a separate tool shelf may be attached at the top of a step ladder.