What is the function of the non-locking screw?
The non-locking screw is intended to be used to help lag the bone to the plate in the event that the plate holding forceps are not effective at doing this. The non-locking screw would be placed in the first drilled hole and tightened down to draw the plate down on to the surface of the bone. Locking screws should be used at subsequent holes, and the non-locking screw should be replaced with a locking screw once all remaining screws are placed.