I do keep the doors locked and give a key to guests/care givers, and they know to do the same. We have our doors with locks on the inside, and we have an alarm system that tells when a window is opened. He has tried to leave several times through doors or windows, so there is no other choice. I do not lock him in alone. If I need to take the garbage out or check the mail, I wait until he is asleep or when someone else here. It is sad and hard, especially when he tries to open the door when he is calm. One day he told our pastor that he is in "jail," and I added that we are both on "house arrest." But, all kidding aside, I am the one solely responsible for his safety, and if I want us to stay together at home, this is one of the solutions to make it happen. This has been a huge help to have the doors locked and all keys hidden and/or accounted for. I also make sure I have a key on me 24/7 - especially if I do run out for a few minutes to get something out of the car, mail, etc., because he has locked me out one time (that was a quick lesson to learn and not repeat). It is sad and just another level of the endless heart shattering that follows the trajectory of the disease, but a necessary element to stay at home.
Treasuring the moments and grateful for others that understand..
Jan