Until the end of the of the 19th century most Highlanders depended on a subsistence economy based of the growing of grain crops such as wheat and barley on unenclosed fields in the glens, and on the grazing of sheep and cattle on the surrounding hills. During the spring and summer the grazing animals were moved up onto high ground, both to keep them away from the growing crops, and to take advantage of fresh growth on the upland pastures. These upland pastures were known as ‘airidhs’, where those tending the flocks would build simple huts or ‘shielings’. The remains of these simple shelters are still to be found on the high ground around the glens of Angus and Perthshire.