A transfer apparatus for receiving the chair seat of a wheelchair and supporting the chair seat in the base of a washing enclosure. The transfer apparatus has a chair support member including a chair support track section that can be positioned in the washing enclosure base, a bridge portion with a bridge track section that is movably mounted to the chair support member. The transfer apparatus includes a lock system usable to secure the bridge portion in an in-use position and engaged with the wheelchair. A first lock inhibits rotational motion of the bridge portion. The first lock includes a retractable locking member that is biased to an extended, locking position. A second lock is usable to prevent longitudinal separation of the bridge portion and the wheelchair. The first and second lock can be automatically engaged when the bridge portion is moved to the in-use position.