The screw and peg will need to be installed outside, since they must go on the side of the door without the hinges. But that’s OK!
The GlideLok is not meant to be a security lock, and it is designed to open from BOTH sides of the door by an adult. That is what prevents you from being locked out accidentally, because many childproof door locks only lock / unlock from one side.
For most exterior doors, you will also need to remove the spacer bar (from GlideLok Part C) with a #2 Phillips drill bit. Be careful to avoid stripping the screws.
