In this video we learn how to remove door material to install a mortise lock. If you live in an older home where you have to take out a chunk of the door to change the lock, there are ways to prevent doing this. First take a spade bit and slide it over the lock. After this, take the mortise lock and hold it so it's flush with the door. Go below the hole and above the closest obstruction and put a mark. On the back measure slightly beyond what it would take for this to bottom out. Once you have these marks you will have the width and depth of your cut to install the lock!