Blogger Nicolas Lellouche went digging in the iPhone Duo settings during his hands on time with the device. He found a curious new option in the display settings called ‘Shift Left Edge’.

When enabled, this setting adds a bit of a black border to the left side, essentially adding fake bezel on the outside screen, pushing content away from the folding edge.

The description for this setting in the iPhone Duo software says that it “moves content when you are using a case that partially covers the left edge of the outer display of your iPhone”.

As you can see from his short demo video, with the setting turned on, it roughly doubles the width of the black border on the left edge of the iPhone’s Duo outer screen.

It’s unclear what kind of cases would require this setting to be enabled.

Apple is offering two first-party case accessories for the iPhone Duo at launch; the iPhone Duo Case and the iPhone Duo Folio with Kickstand.

Without having proper hands on time, it’s hard to tell whether these cases significantly overlap the left edge and obscure the screen content, but it doesn’t seem like it would be an issue. It is possible Apple is envisaging this setting will be useful for other — perhaps more rugged — case designs offered by third-party accessory makers.

We’ll know more closer to launch. iPhone Duo goes on sale next month, on October 23rd.