Abstract: A locking support assembly for a casino chair uses a support plate with a chair mount having a fixed pin protruding upwards from the support plate opposite to the mount. The pin may serve as a sole or primary guide member in the support plate to guide the support plate into horizontal alignment with a latch mounted inside a beam. The beam holds the support plate in close but unlocked engagement by a lower groove, to resist loads imposed by an attached chair. A releasable latch inside the beam receives the pin to provide locked engagement between the support plate and the beam. The beam may be fastened to a vertical surface of a gaming machine or other object. The support plate and attached chair can be released from the beam by inserting a tool through a keyhole in the beam to release the latch, while pulling the support plate outwards.