Three livery companies (the Glaziers and Painters of Glass, Launderers, and Scientific Instrument Makers) share a hall in Southwark, just south of and outside the City of London, while the Worshipful Company of Gunmakers has long been based at Proof House, in the London Borough of Tower Hamlets and the Master Mariners' "hall" is an historical ship, HQS "Wellington", moored on the Thames which is shared by the Scriveners' Company. Companies without halls customarily book use of another livery hall for their formal gatherings, giving members and guests the opportunity to visit and enjoy different City livery halls by rotation.