Each lock is equipped with a key,just adjust the width of lock plate,place it on the upper or lower track of any sliding window or door,rotate the key to secure it and youre done making your sliding doors and windows safe for children,toddlers and pets while improving air circulation in your home without worry.Warm tips:use two lock on heavy duty windows/doors for added security and keep it in place by key control. The use of principles:These slider locks are must-have for any parent that wants to easily prevent your curious little kids from opening the sliding windows or doors to gain access to unsafe area to avoid falling accidents when theyre out of sight!Can fix the window in place, cannot be pulled or opened, effectively prevent your child from opening the windows by his own, anti-theft and keeping the fresh indoor air.By locking your windows, it can also protect your property against damage during heavy rains and hurricanes, or guard against theft and avoid property damage during your traveling period. Wide Usage:Glass security doorwindow stopper can be used with most horizontal or vertical windows and doors to keep them partially open and closed without having to make any major change!Whether you want to keep your doors and windows firmly closed or keep them slightly opened for air circulation,you can count on our security door stops to make sure they stay firmly in place.Perfect for patio doors,sliding glass doors, sliding windows,retractable screen doors,or sliding storm windows etc.