Abstract: A rotary plate fastener (24) is provided for firmly fastening ceiling fan blades (26) to mounting brackets (20). A plurality of protuberant members (32) extend upwardly from the mounting brackets (20), and have respective head portions (72) and shank portions (74) which fit through apertures (62) in the ceiling fan blades (26). The rotary plate fastener (24) has an upper surface (36), a lower surface (38), and peripheral edge portions (42) extending between the upper and lower surfaces (36, 38). Openings (46) formed in the peripheral edge portions (42) are aligned for registering adjacent to the shank portions (74) of the protuberant members (32), and then the rotary plate fastener (24) is rotated to twist the openings (46) around the shank portions (74) and press the rotary plate fastener (24) between the head portions (72) of the protuberant members (32) and the upper surface of ceiling fan blade (26).