rodent fence (or rodent barrier) is a specially-made fence that is meant to keep rodents from gnawing their way into areas where we don't want them, such as gardens. Rodent fencing can be a stand-alone fence, or attached to a regular or deer fence, or can even be sunk into the ground to help prevent burrowing rodents. This type of fencing is typically made from heavier-duty materials (like steel) so that it is effective against a rodent's amazing gnawing ability.
Due to the additional cost of the fencing, homeowners may want to wait and see if rodents are gnawing through existing fencing before purchasing rodent fencing. These products are often the do-it-yourself type and can be installed fairly easily. They are meant to act as a deterrent against rabbit and other gnawing rodents. If you notice burrowing rodents accessing your garden, you may need to extend the fencing below ground level as well. Extend it at least 6" into the ground (more if you need to). It should also extend above ground level to deter the rodents that would gnaw there too.
A rodent fence isn't always necessary. However, it is a good preventive measure to help protect gardens, trees, and shrubs. Another good thing about it is that it removes an attractant from rodents so that they more likely to go elsewhere, and less likely to cause a problem in the yard or garden, or in your home. Prevention is much more preferable to even humane pest control, if given the choice!