An engine room harness routing structure is provided that allows a harness trunk line to be routed without imposing restrictions on the design of the vehicle body. The upper piston part has a top land that runs around its circumference, and a ring belt that runs around its circumference. Each axially-elongated aperture includes a first fulcrum axially spaced adjacent to the cutting edge, a second fulcrum axially spaced further away from the cutting edge than the first fulcrum, and optionally a third fulcrum axially spaced between the first and second fulcrums.