1a ladder and a vertical post suspended perpendicularly from the rung bracket the vertical post is typically sufficiently long to extend beyond at least one rung below the rung engaged by the rung bracket when in place the vertical post rests on the rung below the rung engaged by the rung bracket a two rung ladder jack contains two rung brackets rung bearing brackets an upper and a lower rung bracket each adapted to fit over a rung on a ladder and a vertical post connecting the two rung brackets wherein the rung brackets are connected to the vertical post at an appropriate spacing such that the two rung brackets engage and fit over adjacent rungs on the ladder a three rung ladder jack contains an upper rung bracket and a lower bracket each adapted to fit over a rung of a ladder and a vertical post connecting the two rung brackets wherein the rung brackets are connected to the vertical post at an appropriate spacing such when the upper rung bracket engages and fits over a rung the lower rung bracket engages and fits over a second rung that is two rungs below the rung engaged by the upper rung bracket a three rung ladder jack may optionally contain a third rung bracket adapted to fit over a rung that is between the rungs engaged by.