Gravel boards are fitted between fence posts and under fence panels to stop ant gravel, soil etc damaging the actual fence itself. The image below shows a gravel board fitted to a wooden post in the simplest possible way by fixing a batten to each post and simply screwing the gravel board to the batten. Galvanised clips or Gravel board cleats can be used to fix the gravel boards as they provide a degree of adjustment after fitting. The gravel boards can be fitted to the face of the posts, or even at the back. They can be any size required.
Usually gravel boards are pressure treated, sawn timber but concrete gravel boards are used also. These are available from most builders merchants and fencing suppliers. The standard size tends to be 22mm thick, 1.83m or 6 feet long and 150mm deep. There is no reason why two gravel boards cannot be placed on top of each other to give 300mm of protection.