Every wonder what the furnace sits on in the garage? Ever wonder what’s behinds the sheet metal but don’t want to take off all 35 screws? This is where the indoor coil goes when a furnace is air conditioner or heat pump ready. If no coil is in this box some times the insulation will fall off the side and in to the plenum blocking air to your home. If no coil is in the cabinet and the airway is blocked, it’s worth the time taking off all 35 sheet metal screws to verify the insulation is where it belongs.