This sign is used to warn people who are either unstable on their feet, or just moving around too fast for their own good, that they are entering an area where a solid tiled floor has recently been covered in water, either through an accident or through some cleaning process. This is so that they can take extra care not to fall over.

However, since these signs are usually only a foot or two in height and are placed strategically in the middle of the slippery floor, they are often completely obscured by people's legs and are a major source of accidents.