There are a number of different fencing options, all of which will keep poultry safe and secure. Some are fairly low cost and others are more expensive but all of them will provide a good level of protection. Some are designed for specific predators such as foxes or badgers, and these are particularly effective if they are buried or have an electric wire running around the base.
The cheapest of the poultry fencing netting (also known as hexagonal netting, chicken wire or hex net) and it can be found in most hardware stores. This is a mesh of thin wire, twisted and woven together into a honeycomb pattern so that it looks a bit like a chicken net. It is lightweight and can be used to create a run or small pen. It is not intended to deter motivated predators but it will do a good job of keeping chickens safe and out of trouble.
Secure Your Flock: A Guide to Poultry Netting Choices for Canadian Poultry Keepers
Another option is chain link fence, which will deter most predators and is inexpensive enough to be a very good investment. It does have some drawbacks, however. It can be difficult to keep chickens in, and it is also easy for them to jump over. This is not a problem for most people, but if you have flighty chickens then this type of fence may not be suitable for them.
Finally, there are electrified fences that will work well for poultry. A two-wire system with the first wire being close to the ground and the second one higher up will shock any predators that try to dig or climb over. Alternatively, you could use a mesh netting electric fence in which case all parts of the netting are electrified.