A house number is a number or combination of numbers assigned to a house or building and used to identify it. House numbers are used to locate houses and buildings and to guide visitors to the correct address. In some countries, it is common to place house numbers on the front door or window so they are easily visible to visitors. In other countries, house numbers are sometimes put on a sign or pillar next to the door. House numbers are also often included on maps and in postal and address books to facilitate finding addresses.