Printed from: https://conservationhandbooks.com/dry-stone-walling/variations-in-walling/single-walls-or-dykes/
Walls partly or completely of stonework one stone thick can be found in most areas where large building stone predominates, notably in Scotland and South West England. Single walls are nearly always built of field clearance stone, as opposed to quarried stone, and the rock type is usually igneous, with granite the most common type....