need to lock from outside

Thanks for posting. Due to the design of this handle set, it's a bit tricky to adapt a key lock like our 82-310 to it. In theory it's possible, but you would have to drill a precise hole in your outside pull and file it to be even; it's quite a hassle. We recommend you instead replace the entire handle set with our 82-081, which is the same design as your old handle set but comes built with an outside key lock. Take a look and see what you think.