[HayZee518]

the old door had a mortise lockset and its strikeplate had a rectangular cutout for the latch and a smaller similar shaped cutout for the lock deadbolt. a new passage lockset has a strikeplate shaped like the letter D with an extra cutout on the D side with a notch for the primary pin. you need to remove the old strikeplate, fill in the openings from the old plate, then drill out a clearance for the new bolt. the strikeplate may need to be mortised into the door frame with a chisel so it lays even with the door jamb.