Fence tensioning is an important add-on for deer fence. 

For one, the monofilament wire helps to keep fences nice and taut between posts when spaced closer than the recommended 15-20' feet spacing. Having monofilament wire allows fence to not droop between posts thus preventing white-tailed deer from jumping into growing sites. 

Monofilament wire is also nice to have for homeowners that have trees on their property. If a branch falls on the fence, due to wind or other issues, the fence will remain strong due to the line of monofilament. 

Fence tension wire is recommended at the top of the fence; but it can also be placed at the bottom. When considering deer fence accessories to buy, consider monofilament wire.