Hi,

I'm putting some networking connections and stuff under a trap in the
floor. I want it to be easy to open up for maintenance, but without
any bits of hinge sticking up (trip hazard, unsightly), so I'd like to
pull up parallel sections of three floorboards, screw two of them
together from the underside to make the door, put some kind of
concealed hinges between that and the third board, and screw the third
board back down.

So the big question is: do hinges exist that can be screwed to the
boards' undersides so they are at 180 degrees when the door is closed
but will open even wider (ideally 270 degrees) to open the trapdoor?

(The usual kind of concealed hinges for kitchen cupboards sit at 90
closed and 180 open.)

Thanks for any advice!