This Dreambaby Window Lock is designed for use with inward opening windows, and will limit and restrict how wide the window opens. The lock screws into the window frame, creating a restrictive arm, holding the widow in a certain position. This can provide some safety and make it less likely that your child may fall out. Installation template and screws are included. Polite Customer Notice: this product is for simple baby safety applications and is not suitable as a security lock.