An item that is initially a piece of personal property but is later attached permanently to the realty is known as a fixture and is treated as part of the realty. Thus, if a person rents another's property and installs a built-in microwave oven, the oven is a fixture and becomes part of the realty. The tenant may not remove the oven when he or she leaves. There are two exceptions to this rule. First, the parties may agree that specific fixtures will be treated as personal property. To be enforceable, such an agreement must be in writing. The second exception is for trade fixtures. A trade fixture is a piece of personal property that is affixed to realty in conjunction with the lease of a property for a business. When an entrepreneur opens an ice cream parlor in a leased building, the freezers he or she installs are trade fixtures. These are treated as personal property because of a presumption that neither party intends such fixtures to become a permanent part of the realty. The businessperson will need the freezers at any new location, and new business tenants will have different needs.