Horse fencing can come in 2 different types and used to protect your paddock or surround a schooling area. 

Horse Netting is often used as a boundary line to a paddock. This is just a higher stock netting to stop the horses from jumping over. 

Timber can be used to create a high Post and Rail paddock fence. It is recommended to coat the timber with a creosote after or before construction as this puts the horses off from chewing on the timber and wearing it down. Timber is not just used for a paddock as it can also be used to fence off a schooling area complete with a kick board on the bottom to hold in your woodchip/ rubber flooring if necessary.