These mount under the bottom of a wall cabinet. Ductwork inside an adjoining wall, chase, soffit, or ceiling can exhaust smoke and fumes to the outside. In a few models, a shallow hood slides out of the upper kitchen cabinet when you need it. Typical kitchen cabinets extend only about halfway across the stove, so this extension routes steam and smoke away from cabinet faces and back toward the suction end of the range hood. This design steals cabinet space, but might be the only choice for those who cannot achieve the recommended stove-to-hood clearance with a standard under-cabinet-hood design.