From the Anvil Black Octagonal Mortice/Rim Knob Set

 

These mortise /rim knobs come unsprung. They are solid cast not hollow and have loose roses to enable them to be used with a rim lock (discard one rose) or with a mortice lock.

 

They have treaded spindles to take the adjustment for various door thicknesses and lock firmly with a grub screw. Each set comes complete with fixing screws, which are concealed for improved appearance, together with two escutcheons.For best results the centre of the knob should be a minimum of 3' from the edge of the door. Heavy duty latches and locks are recommended for maximum efficiency - see codes 18299/4' or 18238/5'. Please note that all the knobs with this traditional black finish range can be used externally. 

Sold as a set and supplied with necessary fixing screws. The GRUB SCREW should locate on the 'V' in the shaft and not on the threaded part.