number plate bulb

Whats the score with changing the bulbs for the rear number plate, there appears to be 3 screws holding the unit in, i undid the middle one expecting it to flip down or something but it just slid about a bit, do i have to undo all three or is there an easy way?

Slide it towards the screw ,away from the lens ,there's a L shaped hook opposite .You may find it all desintegrates once you have the unit apart though