In my line of work I will have a system loaded , shut down ready to deploy to the end user. And will realize that I left a cd in the CD ROM drive. Straighten out medium size paperclip, insert it into the small hole in the front of the cd rom , there is a little lever inside that you can push and the tray will pop open. It takes a little fishing around to find it but its there
it is less that an half inch in depth so dont push a whole paper clip in there