Top Vent

If there’s a 6” vent pipe inside the cabinet (above the range hood) then that’s top vent. The vent pipe can be vented out through the roof, the back wall and the side wall to the outside.

Rear Vent

If there’s a 3 1⁄4” x 10” opening locates below the cabinet then that’s a rear vent. The opening sometimes can be seen just by removing the bottom screen filter of your existing range hood. If you have a microwave range hood, you need to remove it to see the opening.