Removing Solair 101303 Patio Sliding Door From Frame?

[dilligaf76]

Does anyone know how to remove a patio sliding door fitted roughly in 2002 from it's frame. I know I have to raise the rollers by turning the screws as to give the door clearance from the bottom and top rails but problem I can't seem to overcome is the 3 inch L shaped security block at the bottom of the door in the middle is screwed down which prevents you from swinging the door out.
The problem is I cannot unscrews these because they seem impossible to get to as they are directly under the door?