The Magic Button top of the Philips exDVD-RW drive!

i just bought ed16dvdrk philips external dvd writer. I noticed a big button top of the its cover. It is bigger than the tray button and its double clicks when i pressed. But i cant find any info about the button in manual…Does anyone know what is the function of the button??? :confused:
please check attached the picture

It squirts cream into your coffee. Dont forget to refill it.

The “button” holds the two parts of the casing (black and grey top part) together…