How to envision hook design and no hook design :1) Touch the tip fringe of the door with your arms to peer if there's a latchhole as under comment .2) Or When the door lock is in the pop-up state, whether there's lock latch at the height fringe of the door come out ?If height edge no latchhole ,then favor no hook design ,Or PLS choose hook design .About Size: This lock is for length No2: 30mm, If for brand spanking new door ,then may perhaps forget about it .1. Using 1 small pin to push the spring up as comment No1 ,when see the latch No2 up ,then trun the latch directly at the same time .Soft note:1. Description :1) Material: iron shell2) Color: Black3) Size : 60/68 as above size4) Features :Anti-theft ,Anti-pry ,Anti-Violence open door lock part2.Transition:1 cm = 10 mm = 0.39 inches3.About shade :Depending on the light and the screen, the color of the thing could also be barely various from the color of the picture.4. About the size :Allow 0.5-2cm distinction because of guide measurement5.About massive order :if there may be big order ,welcome to touch us free .TKS .