Installed elevators to horizontal stabilizers. Clamped leading edges. Applied welding clamp to elevator horns to secure alignment. Removed leading edge clamps and positioned elevators so 5/16th" hole could be drilled through horns for elevator push/pull rod clevis installation. Drilled and reamed. Removed elevators from plane, cleaned finished hole, placed elevators on flat surface, clamped horns and removed material to fit clevis. Reinstalled elevators to plane.