According to the Humane Society of the United States, there are an estimated 90 million cats in North America, and more than 30 million households have at least one cat. Pet owners are advised to keep their cats indoors for a simple reason: Indoor cats have survival rate that is five times greater than outdoor cats. Roaming cats can break into garbage cans, dig up flower beds and defecate in children's play boxes, proving a health and safety hazard. Outdoor fences for cats---also called cat enclosures or cat-proof fences---are systems that enclose a part or the entire portion of an owner's yard---allowing outdoor access to the cat within the safe confines of the yard. Most feline containment systems are either affordable do-it-yourself projects or professionally installed.
A free-standing cat fence is made of lightweight, flexible polypropylene mesh grid that is strung between poles (usually made of metal). The fence is put up around the boundary of the property to enclose it completely. The top of a free-standing fence is curled inward, so even if a cat manages to climb the mesh, it will simply fall back down.
Fence-top systems are a strip of thick wire mesh that is added to the top of an existing fence. Outdoor fence systems can be easily installed, and fit on any height and fence surface---including wire, masonry, vinyl and wood. They come as safe/narrow, strong/flexible, non-electric or almost invisible systems, all designed to keep a cat safe and prevent stray cats from venturing inside.
The electric fence is among the oldest type of cat containment fence. It works by supplying a small electric current through a wire buried underground. The fence works in conjunction with a receiver that is attached to a collar for the cat. The receiver emits a loud warning sound every time the cat approaches the fence. The cat is given a small dose of current if it ignores the warning and succeeds in touching the fence. The electric fence is currently under debate and its safety is being studied by the United Kingdom's Department for Environment, Food and Rural Affairs.
An ingenious, and relatively inexpensive, way of keeping cats within an enclosure is by running 4- to 6-inch PVC pipes over an existing wooden or chain-link fence. The pipe prevents an adventurous cat from getting a firm grasp and keeps them contained.