In the USA, a carpet will generally be 12 or 15 feet wide and in Europe it will be either 4 or 5 meters wide. Where needed, different widths can be seamed together with a seaming iron and seaming tape. The carpet is fixed to the floor on top of a cushioned underlay and is fasted using nails, tack strips, adhesives or decorative metal stair rods. The use of wool, natural padding and formaldehyde-free glue is becoming more common due to environmental reasons. Though environmentally friendly options do not sacrifice performance or quality, they do come at a premium price. In the UK some carpets are still made with 27 inch widths and then sewn to size for use in pubs and clubs. Carpeting is a term that covers the carpet itself, the carpet backing, the cushioning underlay as well as the method of installation. Carpet tiles are generally a 50 centimetre square and used in commercial settings.