Unplug your Black & Decker Hedgehog and place it on a work bench or flat, stable surface with the blades pointing away from you.
Use a pair of pliers to loosen the bolt on the Hedgehog's blade runner by turning it counterclockwise. The bolt will be located on the Hedgehog's snout, near the electric motor.
Put on a pair of leather gloves and pull the blade off the Hedgehog. File the teeth with a metal file to sharpen the blade. Run the edge of the file across each separate tooth along the blade. Apply enough pressure to sharpen but not too much or the file will cut into the teeth and chip the blade. Each tooth should sharpen in about 1 minute of filing.
Test the sharpness of the blade by dragging it over a sheet of paper. If the paper cuts without applying pressure, the blade is sufficiently sharpened. Oil the blade runner or snout and replace the Hedgehog's blades. Replace the bolt and tighten it.