You will need a drill with a hole saw bit of the right size for the lock cylinder. You’ll also need drill bits of the right size to drill pilot screw holes. You may also need a router to help cut the mortise area into door to allow the faceplate of the bolt or latch part of the lockset to fit flush against the edge of the door. A good, sharp chisel will be needed to help cut the mortise area tidily. You will also need a pencil for marking out, and a square and ruler.
The Backset Size
This is a vitally important thing to know to buy and fit the right lockset. Essentially the backset is the distance from the door edge to the center of the lock cylinder where a handle spindle passes through a door.
Fitting the Lockset
Mark out the back set distance for the door edge with the pencil and ruler or square. Draw a line round the door edge and check that it is square too so that the bolt or latch will line up in the right spot.
You will also need to mark out the proposed mortise areas and a template may be provided with the lockset for this. Mark out the position on the door frame too for the strike plate.
Use the appropriate size saw hole bit to drill out the hole for the cylinder in the door. You may want to clamp a piece of ply to the other side of the door while you’re drilling in order to stop the edge splintering. Drilling from both rather than just one side can also protect from splintering.
Put tape around the drill bit to the required depth for the bolt and drill straight into the edge of the door up to the tape line.
Use a router and chisel to cut out the mortise area and drill pilot screw holes.
Fit the barrel and bolt into the holes as per the lock instructions and screw into the door.
On the door frame use the appropriate sized hole saw but for the jamb in the strike plate and use a router, chisel and drill bits to cut out the mortise area for the strike plate and for the pilot screw holes.
Screw everything in and test the lockset.