Abstract: A cover (3) for mounting on a frame structure (1) associated with a manhole, the frame structure (1) having side walls defining a central opening there through, the cover (3) including: a cover member dimensioned to fit the central opening with a bottom surface of the cover member facing towards an interior of the manhole and a top surface (9) of the cover member facing away from the manhole, the cover member being moveable with respect to the frame structure (1) between a closed position, whereby the central opening is covered, and an open position, a lock mechanism for releasably locking the cover member in the closed position, the lock mechanism including one or more locking members (13) engagable with the frame structure (1) to thereby retain the cover in the closed position and a lock actuator connected to the locking members (13) for engaging and disengaging each locking member (13) with the frame structure (1), the lock actuator being accessible from the top surface of the cover member, the lock mechan