I am trying to figure out if there is a way for me to have a solution for the following dilemma, without cutting in a separate lock into the hinged patio door (which I will not do as it would void my 20-year warranty).

The reason why I want to install a lock with keys from either inside or outside is because we have a small child and we don't want him to be able to sneak into the room, turn the knob and get himself out on the balcony. In addition, we don't want him to be able to lock us out while we are on the balcony. Anyone with kids would understand our concerns.

I have spoke to Andersen and they told me that they do not sell a lock with a key on both sides. The representative did tell me that their locks are 1 3/8", and that the locks are made by Schlage for Andersen.

Here is the technical background of what I have:

My door is a 400 Series Frenchwood Hinged Patio Door (1988-present)

http://www.andersenwindows.com/~/media/aw/files/technical-docs/parts-catalog/partscatalog-patiodoorsincludingstormwatch-1988-present--400series-frenchwoodhingedinswing.pdf

The doors handle that we have is called Anvers. Currently, there is no security lock installed. You can see the Anvers hardware parts breakdown on page 72 in the above link or here:

http://www.allaboutdoors.com/popup_image.php?pID=2578915

http://www.allaboutdoors.com/popup_add_image.php?imagesID=3229

Here is the lock that is sold by Andersen for my door:

http://www.andersenwindows.com/~/media/aw/files/technical-docs/accessory-guide/accessoryguide-0005155.pdf

As you can see, it has a turn knob on one side and the key on the other, which is not what we need.

I realize that some adjustment would need to be made (like a different plate) in order to make this happen if a compatible lock could be found. But as long as its done in the area of the door handle, we don't mind it.

I guess the worse case scenario would be to use the standard Andersen lock, but reverse it (knob to the outside, key on the inside) and then completely removing the knob, blocking the open hole and not having anything there so no one can lock/unlock the door from the outside at all, but we would be able to open or close it from the inside with the key.

If anyone has any ideas or input into this situation, I would appreciate it!