NWOT - Special Design---Special double button design with soft TPR material increased friction with the door knob. When you need to open the door,press the double buttons and turn the door knob easily. Easy Installation/Removal---No Adhesive, no drill and tools need,no harm to the door.Take off the door knob cover then set it on the door knob and close the two covers,the door knob is in lock.It can be easily removed by a screwdriver. Why need it---Prevent babies from opening the door and getting into dangers like the kitchen & toilet or the storeroom and get injured;Prevent babies from going in or out of the house without adults' superision; Prevent children from playing with the door and pinching their fingers.