Certain design alterations are made when a living or work space is likely to be used by persons with disabilities. Handicapped residential units, hotel and restaurant bathrooms, and other hospitality institutions equip bathrooms, showers, and entryways with handrails, special hold bars, and so forth. A transition between two different flooring surfaces must also be made safe for passage.A transition threshold is a strip of material placed at this junction, usually in a doorway. Where tile meets carpet, for example, the threshold provides an efficient water barrier while at the same time making it easy for foot traffic or wheelchairs to safely pass. Designers of home and commercial interiors often specify marble or other natural stone as the preferred transition material.