Using eye protection! Take a punch and strike the center of the bolt inside the six sided hole, not on the face of the bolt, rather hard several times. Then take a pointed punch on the face of the bolt outside of the six sided hole on the flat part in the direction that you want the bolt to turn. If you can, have a helper wearing EYE PROTECTION apply moderate torque using the bit in the six sided hole while you strike it around in the loosening direction. It will come out.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer