The above photos shows Larch Tongued and grooved wall top Fencing being used as a side panel to a gate (Larch is no longer available). 

Tongued and grooved Fencing is a strong, smart and solid fence.
As with most wall top fencing it is fixed to independent full height posts behind the wall it adds no strain to the existing wall structure making it perfect for older walls.
Constructed on site it is available to any height , shape and formation.