A grating fastening device comprises a base member (22) on which is mounted a saddle clamp (24) and a swivel clamp (26). The swivel clamp is rotatably mounted on the base member and is spring biased perpendicular to the base member for ease of installation. The fastener is easily installed by rotating the swivel clamp parallel to the base member against the spring bias, inserting the assembly between two adjacent bearing bars, and allowing the swivel clamp to spring to its engaged position automatically engaging the bottoms of two adjacent bearing bars. The saddle clamp engages the tops of the same two bearing bars engaged by the swivel clamp, and is arranged centrally of the base member, the swivel clamp being arranged at one end and the other end (64) of the base member being adapted to engage an under surface of a grating support (16), so that the forces on the base member are balanced.