the purpose of the coping stones is to add weight to the top and also to help shed rain to the sides
when they are all leaning on each other they lock together well
I want to build with stone and lately I have been on a kick of watching videos in the evening
some I have been watching lately are
dry stone tv:
Eugenio Monesma:
Brian Post:
Vermont heritage granite company:
this video is interesting as well:
look through each channel and there are more good videos
there are more I want to post but would have to do some searching... when I find more good ones I will post here