The deadbolt should be a circular piece of metal, anywhere from a few inches to a few feet directly above the doorknob. The deadbolt functions just like the doorknob, but it uses a different key and its bolt is much heavier. On the outside of the door, the deadbolt should look like another keyhole. On the inside of the door, the deadbolt should feature a heavy, rotatable switch. A locked deadbolt will keep the door from opening even if the doorknob turns.

If your door doesn't have a deadbolt, do not worry. A deadbolt is not an essential security feature, although it will make your door even harder to break through.
 If you have a key for the deadbolt, use it. This key should be different from the key that fits the doorknob. Close the door and stand outside. Slide the key into the deadbolt keyhole and turn it clockwise as far as it will go. If you turn the key far enough, the door should lock.

To remove the key, turn it counter-clockwise back to the position at which you slid it in – but no further! Pull the key out of the keyhole.
Try to turn the doorknob and push the door open. If the door will not budge, then you have successfully locked the deadbolt. To unlock the deadbolt, simply turn the key counter-clockwise as far as it will go – just like the doorknob.
 You don't need a key to lock a deadbolt from the inside. Locate the twistable switch on the inner side of the door. Turn the switch clockwise as far as it will go. This should slide the deadbolt into place.

To unlock the deadbolt, simply turn the switch counter-clockwise as far as it will go. This will retract the heavy deadbolt back into the door.
 This can be a great way to lock down your house if you are especially concerned about security. Assess your need for privacy. A deadbolt will make your door harder to break through, but it also means another key to keep track of.

Consider hiring a locksmith to install a deadbolt. The process can be tricky if you are not experienced with locks or woodworking, You don't want to damage your door!
Check your door for a deadbolt.
Lock a deadbolt from the outside.
Lock a deadbolt from the inside.
Consider installing a deadbolt.
{"src": "wikihow-all_validation", "title": "How to Lock a Door2"}