Abstract: A cover insert for spanning a gap between two boards in a decking, in particular a scaffold decking, to prevent objects from falling through said gap and causing injury comprises first and second substantially parallel side walls (10, 11) for fitting into the gap and a cover portion (7) arranged for covering the space between the side walls. One of the side walls (10) has a pair of laterally extending walls (9, 13) extending outwardly in a direction away from the other of the side walls, the laterally extending walls (9, 13) being spaced apart for receiving an edge of one of the boards. A top one of the laterally extending walls (13), that may be an extension of the cover portion (7), provides a flange that rests on the top of the board on one side of the gap, and the cover portion (7) may also extend on the other side to provide a second flange (14) to rest on the top of the board on the other side of the gap.