All walls need to be capped correctly.  This is not only aesthetic, but also practical.  

Cock and hens add weight to the wall, creating stability also creating a barrier to prevent it being climbed.

Drystone walls often use a spill stone, slightly over hanging the top of the wall on both sides, with a line of larger rectangular stones on top along the middle of the wall, creating stability.

There are lots of different ways of doing the coping, depending what you are looking at achieving.  Within the the drystone walling stone from Stalbridge Quarries, there is normally a good mix of stone that can be used to top a wall off.   However depending on the design, there may need to be some extra stone.  Speak to Jimmy to discuss the design of the wall, and what is required.