A stile is a device which allows people to cross a wall, fence, or hedge without allowing livestock through. Stiles are typically designed so that people do not need to open a gate or move any parts, simply walking over the stile to reach their destination. The design, however, is unfriendly to livestock, ensuring that livestock cannot escape over the stile. The “stile” has also been adopted in the sense of the turnstiles used in places like subway stations to control entrances and exits.
In the most basic form, a stile is simply a set of ladders which run over an obstacle, so people can climb over. Other stiles take the form of steps, specially designed gaps in fencing, or ramps. If you've ever wondered about a strange structure in the middle of a fence, wall, or hedge, now you know what you were looking at! A related concept, the kissing gate, is a gate which requires force to open, along with a narrow body to navigate the gate's enclosure, and closes on its own.
The goal of both kissing gates and stiles is to allow people to pass through a landscape with ease, without increasing the risk of livestock escapes. When people pass through gates, they may forget to close them, or close them improperly, allowing the animals to get out. It's impossible for animals to get out over a stile, and stiles are easy for people to use, making them popular with farmers and walkers alike.
In nations like England where people are permitted to walk on farmland and many parks and estates, stiles are used to make footpaths easier to navigate, and they may be required by law along well-established paths. People may also use stiles around the home or farm to create a way to pass over a fence or wall without needing to build a gate, since stiles are easier to construct and maintain than gates. While a stile does require periodic maintenance to ensure that it is not rotten or dangerous, it doesn't require nearly as much work as a gate.
Using a stile usually requires full mobility. For this reason, some disabled people have criticized the widespread use of stiles, arguing that stiles impede their access to public footpaths. The need to accommodate people with disabilities is recognized and respected in many nations, but farmers have fought against the installation of gates and other workarounds, fearing that disabled-friendly passages would be easy for livestock to navigate. A cow, for example, can go in most places a wheelchair can travel.