A wall consists of the vertical structure, or “stem,” and a horizontal support, which is the foundation—usually built of concrete. There may also be a separate top, either a cap or a coping, which has the function of casting off water. It may be more impermeable than the stem of the wall, and may also be an aesthetic choice. A coping should project beyond the face of the wall, while a capping is flush with the wall surface.
A cheap, cast-in-place concrete wall can be stonecapped, and the use of this relatively expensive capping material can give the wall a pleasing visual “trim.”
It is also possible to use a metal-sheet capping of zinc or stainless steel—or one made of bricks on edge, whether in the same brick as the rest of the wall ...