A stile is a structure which provides people a passage through or over a fence or boundary via steps, ladders, or narrow gaps. Stiles are often built in rural areas or along footpaths to allow access to an adjacent field or area separated by a fence, wall or hedge. Unlike a gate, there is no chance of forgetting to close it, but they may well be difficult to use for some disabled people and people with limited mobility.
In the United Kingdom many stiles were built under legal compulsion (see Rights of way in the United Kingdom). For that reason a wide variety of designs exist. Recent changes in UK government policy towards farming has encouraged landowners in upland areas to make their land more available to the public, and this has seen an increase in the number of stiles and an improvement in their overall condition. However, on popular paths, stiles are increasingly replaced by gates or kissing gates - or, where the field is arable, the stile can be removed altogether, as there are no longer any animals to control.
Stiles also sometimes have a 'dog latch' or 'dog gate' to the side of them, which can be lifted to enable a dog to get through (see pictures below).
There is a British Standard that includes stiles BS5709:2006 Gaps Gates & Stiles (ISBN 0 580 48107 7). It says "New structures shall not be stiles unless exceptional circumstances require them".