Designs for shower facilities vary by location and purpose. There are free-standing showers, but also showers which are integrated into a bathtub. Showers are separated from the surrounding area through watertight curtains (shower curtain), sliding doors, or folding doors, in order to protect the space from spraying water. Showers with a level entry wet room are becoming very popular, especially due to improvements in waterproofing systems and prefabricated components. Best practice requires a waterproofing material to cover the walls and floor of the shower area that are then covered with tile, or in some countries with a sheet material like vinyl.