Copings
Coping consists of the capping or covering of a wall. A splayed or wedge coping slopes in a single direction; a saddle coping slopes to either side of a central high point. A coping may consist of stone (capstone), brick, clay or terracotta, concrete or cast stone, tile, slaye, wood, thatch, or various metals, including aluminum, copper, stainless steel, steel, and zinc. In all cases it should be weathered (have a slanted or curved top surface) to throw off the water.
The coping system should be designed to resist impact by displacement or pressure of ladders, or by normal wind conditions.Since a mortar bed alone, would not resist displacement, then clearly parapet copings should be mechanically fixed.