Abstract: A tie-down adapter for attaching a monument, such as an aircraft monument, to a floor structure, such as an aircraft cargo compartment floor. The tie-down adapter includes a base and a stud protruding from the base. The base includes a plurality of fastener through holes configured to align with an existing threaded hole pattern in the cargo compartment floor. The stud is configured to penetrate a mount opening of an attachment bracket on an aircraft monument to be attached. The stud has a threaded shaft configured to receive a fastener for fixing the tie-down adapter to the monument attachment bracket. The tie-down adapter can be provided in a system, and used in a method for mounting aircraft monuments to a cargo compartment floor.