continue to have outdated laws prohibiting electric fences to prevent agricultural fences from entering the city. Houston in Texas for example, changed their ordinance that prohibited electric fencing in 2008. Introduction of high tensile (HT) steel fence wire in the 1970s in New Zealand and in the 1980s in the United States. Introduction of synthetic webbing and rope-like fencing materials woven with fine conducting wires. Design of moveable fence components, such as Tumblewheel, a moveable fence post used for making mobile one-wire fences for the purpose of rotational grazing. The insulated central hub enables the line to maintain power while the fence is being moved. Uses Agriculture Permanent electric fencing is used in many agricultural areas, as construction of electric fences can be much cheaper and faster than conventional fences (it uses plain wire and much lighter construction, as the fence does not need to physically restrain animals). The risk of injury to livestock (particularly horses) is lower compared to fences made of barbed wire or certain types of woven wire with large openings that can entangle the feet. Its disadvantages include the potential for the entire fence to be disabled due to a break in the conducting wire, shorting out if the conducting wire contacts any non-electrified component that may make up the rest of the fence, power failure, or forced disconnection due to the risk of fires starting by dry vegetation touching an electrified wire. Other disadvantages can be lack of visibility and the potential to shock an animal passing by, who might accidentally touch or brush the fence. Many fences are made entirely of standard smooth or high-tensile wire, although high quality synthetic fencing materials are also beginning to be used as part of permanent fences, particularly when visibility of the fence is a concern. Conventional agricultural fencing of any type may be strengthened by the addition of a single electric line mounted on insulators attached to the top or front of the fence. A similar wire mounted close to the ground may be used to prevent pigs from excavating beneath other fencing. Substandard conventional fencing can also be made temporarily usable until proper repairs are made by the addition of a single electric line set on a "stand-off" insulator. Electric materials are also used for the construction of temporary fencing, particularly to support the practice of managed intensive grazing (also known as rotational or "strip" grazing).