This is a JOLIK door lock stopper. It is a safety device to prevent children from accidentally opening doors. Please search for "JOLIK door lock stopper" and you will find similar items, which will give you an idea of how it is used. I used this when my child was young, but I am selling two of the four that came in the set because they were not used. It is a safety item that prevents accidental opening and closing of door handles, and prevents children from operating them incorrectly. The device is fixed with very strong 3M double-sided tape. It is very strong, so I do not recommend attaching it to wallpaper. The length is 12 cm and the lock part is 7 cm high. Please be sure to search on the internet. You will find easy-to-understand explanations. We recommend using this for places where opening the door could be dangerous! #child #doorlock #doorcloser #security #accidentprevention #danger