All garden walls need to be capped correctly.  This is not only aesthetic, but also practical.  There are numerous different methods depending on local tradition and or practicalities. 

Cock and hens add weight to the wall, creating stability also creating a barrier to prevent it being climbed.  They also look impressive and are a practical method of often using bulkier stone that would not sit well within the wall itself.

Another method of finishing a wall is using a spill stone.  The spill stone is flat and slightly hangs over the top of the wall on both sides.  If the spill stones are small, and do not cover the top completely, they can be capped off with a with a line of larger rectangular stones on top creating stability, and covering gaps.

There are lots of different ways of doing the coping, depending what you are looking at achieving.  Within the the dry stone walling stone from Stalbridge Quarries, there is normally a good mix of stone that can be used to top a wall off.  Garden walling is smaller, and so there may not be the mix of stone needed.  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.