EE was attempting to straighten 12"" U Bolt using a frame press with bottle jack attachment. EE turned U bolt on side to compress/reform bolt with a 4x4x2 piece of wood as a brace. When EE released bottle jack the stored energy caused the 4x4x2 piece wood to eject from the press, striking the EE in the face.EE was sent to emergency room for stitches.