There are good examples of horizontal water mills, also known as Norse or Clack Mills, around Dutch Loch. Originally these were two story buildings with turf roofs, built into banks to give access to the upper floor where the mill-stone was sited. Inside the building there was a fixed lower millstone, and a rotating upper millstone driven by the water falling onto the paddles below. Some were still in use on Papa Stour in the early years of the 20th century, and there is still a working example of one of these mills on the Burn of Clumlie, at Troswick in the south Mainland of Shetland.