OK, I have a vinyl-sided patio sliding glass door. I would like to install a mortise-key lock that I can key in from the outside. I have found the right hardware online. However, I need to create about a 2" long mortise opening on the side to enable to "tongue" to come out and hook onto the catch. I can't seem to find any capable locksmiths in my area who are up to the job. How can I cut a mortise opening on the side?