I don't have one, but this video seems to imply that if you put the key in the socket, and turn it clockwise, the battery is connected. If you turn the key counter-clockwise and remove it, the battery is disconnected.
Like this, if this is what you have...
https://www.youtube.com/watch?v=-0CedAjJh7MIn this context, it's also a theft prevention device.
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)