Adding exterior lock on Andersen sliding patio door

Why do you need an exterior lock and the Andersen patio doors? If the door is keyed, spend the fifty.

Do not alter the doors, void the warranty, just to be cheaper.

I used Schlage cylinder to put a lock in my Andersen Frenchwood sliding doors.

Nope, Just break down and spend the money so you don't void a warranty. Its amazing to me that a door that's worth 2500.00 and you won't spend 50 freaking dollars to make it right. I hope you never have to change the hinges on an Andersen French door. Your talking hundreds or dollars

Its not exactly $2500. The door is 20 years old, Permashield white. If this was a brand new door, I would understand. Just asking if there was an alternative. For example, any lock would fit on an entry door. I thought patio doors were similiar.

The interior lock and latch mechanism is on the door already. The exterior lock is just a cylinder that gets bolted on to the interior lock by drilling 3 holes.