Some desks have the form of a table, although usually only one side of a desk is suitable to sit at (there are some exceptions, such as a partners desk), unlike most usual tables. Some desks do not have the form of a table, for instance, an armoire desk is a desk built within a large wardrobe-like cabinet, and a portable desk is light enough to be placed on a person's lap. Since many people lean on a desk while using it, a desk must be sturdy. In most cases, people sit at a desk, either on a separate chair or a built-in chair (e.g., in some school desks). Some users stand at their desks using higher standing desks.