Model of a Ladder

Model of a two-part ladder. The extendable part has a wheel at the top of each leg and is extended with a crank and windlass at the bottom of the component: the rope from this runs over a disc in one of the upper rungs of the component to the lower rung of the extendable part. Two stops prevent it from sliding back. The extendable part is also equipped with a stay, which serves as a support and as a prop. The stay falls out automatically at a certain height; the stay is incomplete.