Before getting started, you will need to know the following:

• The measurement from the middle of your door handle (if you have one) to the middle of the keyhole
• The measurement from the middle of your cylinder to the edge of the door (this is called the backset)
• The measurement of the thickness of your thumbturn or key (depending which you have) and how far it protrudes from the edge of the door
• Any markings on your cylinder, for example, any star markings and the amount of stars