Model of a ladder, Peter van der Loo, c. 1850 demonstration model Model of two -part ladder. The extendable part has a wheel at the top of each leg and is extended with a crank and Windas at the bottom of the part: its rope runs over a disc in one of the upper sports from the part to the bottom sport of the extendable part. Two piles prevent it from moving back. The extendable part is also equipped with a swoop, which serves as an intermediate support and as out holder. The swiling automatically falls out at a certain height; The swoop is incomplete. The Hague wood (plant material). brass (alloy)