Apple has a dedicated key for that purpose on the keyboard (or the OS uses F12 on other keyboard brands)...
a particulary handy feature if the OS is convinced that there
is nothing worth opening...

(you must know that for 'style's sake' the physical ecect button is completely unaccesible)
you have to reboot the machine to get access to the drive again - did this countless times with a Dual G4, maybe they named the model 'Mirror Door' to ironically point to this 'feature'...
cheers, Tom