Here's a cool way to replace the bolt lock on your Barth without much modification. This electronic lock allows the use of a conventional key, or you can unlock with a code you apply. It also allows locking with the push of one button, which has meant I can allows walk out at night and lock up (or unlock) without having to find the door key.

I bought several styles of this type of lock on EBay, before finding one that replaced the lock without cutting, or extra drilling near the lock. This was critical as the Barth lock is complicated and does not allow any mounting near the lock mechanism. I also needed the inside part to be narrow enough to still close the screen door. This model did a great job, with one exception - I needed to mount the key pad upside down to allow the electronic cable not to be pinched. I may powdercoat it black as I'm not real fond of the brass, but otherwise I love the functionality.