We have to choose different lock cylinder for different doors and using conditions.
Cylinder with one side knob and one side key, open or lock the door by operating the key from the outside, or turning the knob from the inside. Generally used for interior door and fire-rated door, it’s the most common cylinder type in the market.
Double side key cylinder, we can use the key to open or lock the door from the both side.It’s mainly used for high security doors, such as the entrance door.
Bathroom cylinder is the cylinder one side with knob and the other side with slot, you can open the door by turning the knob from the inside, or rotate the slot by a screwdriver from the out side, it’s used for bathroom doors.
Half cylinder, one side with key, can only open by key from the outside, generally used for the repair and maintenance doors or storage room doors.