What forms of hard labour were used in Scottish prisons?

In the course of the 19th century the addition of hard labour was increasingly used by judges for certain offences. The treadmill, the hand crank and picking oakum were all used in Scottish prisons. The treadmill was a large drum with projecting wooden treads on its outside and connected to something to provide resistance, which had to be turned by tramping on the treads. The hand crank consisted of a handle projecting from a large box, which had to be turned a prescribed number of times a day to overcome the resistance of gravel or sand in the box. Both were hard but totally unproductive work. A more productive form of hard labour was picking oakum, i.e. teasing out old tarred rope into strands, which were used for caulking ships. The treadmill and hand crank were abolished in Scottish prisons in 1898.