Here’s What Every Hole on the Apple Watch Series 4 Is for

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 Slot Under Watch Band (Bottom)

Lastly, we get to the bottom of the Apple Watch Series 4. Here, you’ll find a curious and mysterious slot that almost looks like it could be a cover for a port.

That’s largely because it is. The physical feature is a cover for the Apple Watch Series 4’s 6-pin diagnostic port, which could be used by Apple staff and service technicians to connect the wearable to repair machines or access hidden and demo features. Its exact purpose is relatively unclear, however.

On that note, we do not recommend that you go messing around with the port. It’s undocumented and messing around with it could lead to unexpected consequences on your device (including a potentially voided warranty).