THE PILOT ELECTED TO MAKE A LOW APPROACH OVER A GRAVEL BAR BEFORE LANDING. HE STATED THAT WHILE ROLLING OUT OF A TURN, THE ELEVATOR CONTROL JAMMED TO THE RIGHT. SUBSEQUENTLY, THE AIRPLANE SPIRALED TO THE TERRAIN, THEN CRASHED. AN EXAMINATION REVEALED THAT A SET OF CHANNEL LOCKS HAD SLIPPED UNDER THE FLOOR BOARD AND INTO THE FLIGHT CONTROLS.