Plain wire has, among others, the following applications;
Top strand to your fence
Bottom strand under the netting. This is also useful for marking out the fence line.
Plain wire fencing. Usually used in conjunction with steel droppers to keep the lines apart.
Can be used to increase the height of your fence.
As a tie wire when wall top wiring.
Used as support wires for vines and other plants.
Available in high tensile, mild steel and spring steel and in spools up to 100kg