Kev what you do is drill four holes 8mm dia, so the threaded insert will fit in, you have to remove the spikes, the flat piece then sits over the hole, i used some araldite, when i did the final fix, i put it on the top of the inserts & on the metal plate so that if by any chance a screw came out, it would stay there, you will need four of those inserts with a 5mm thread, & four m5 x 30mm ( what ever you shelf thickness is ) counter sunk machine screws, so that the plate can rotate side to side when fixed.