IWC sliding door lock

Hey George. It looks like your outside pull has a punch hole meant for a key lock. I believe you could remove that punch hole with a punch out tool, then install a key lock like our 82-310. You'd need to cut the tailpiece, or spindle, of this key lock to the correct size so it works with your door's mortise lock correctly. The video below shows how to do this for a slightly different lock setup--the principles regarding how to cut the spindle are the exact same, however.

Alternatively, you also could just purchase an all-new handle set with the key lock already built in: see our 82-030A. Let me know if you have further questions! 

My pleasure! Let us know if you have further questions, and thanks again for reaching out.