Danny Woodward (who is working with me this summer) is topping off a retaining wall we have built with a Cornish hedge type of coping. It is a bit unusual. The copes are laid on end and create a flat surface which then be covered in sod. The turf on the terrace side will come right over the top of the wall rather than have the usual border of flat stones that one sees in most dry stone retaining applications.
Below is a wall Danny built last year in Furry Creek B.C. built with local basalt.
This time the garden soil stops flush with the vertical copes. Sometimes its nice to have the copes sit higher than the level of the terrace too.