A mobile office is a large temporary structure typically used at new construction sites or disaster recovery sites for administration purposes. Healthcare organizations or retail companies can use mobile office rentals for temporary off-site applications such as pharmacy or grocery distribution. United Rentals Storage Containers & Mobile Offices customizes rugged steel containers with everything needed for a temporary office, such as windows, insulation, lights, electrical outlets and more to meet your needs. Mobile offices can be constructed on trailer-mounted containers, called office trailers, or ground-level office containers.