The knock and drop saw of the Open Air Museum is one of the few still functional saws of this kind still standing. Built in 1673, it was in operation until it joined the museum in 1963. With every revolution of the waterwheel, the frame and its blade is knocked upwards, with the help of cogs on the shaft. This causes a loud knocking noise which is audible far away. Trunks of up to 6m long could be sawn on this saw. It took about 45 minutes to produce one plank. During the 18th century, the knock and drop saw was gradually replaced by the more efficient cranksaw.