[slimomatic]

There are 4 1/4 inch hex head bolts going across the back of the furnace at
16 inches off the ground.
Im assuming they attach the outer casing to an inside frame.
One the inside bolts I can't tighten & the furnace makes a lot of noise.
The other 3 bolts are fine.
How do I refasten this bolt to the frame?
Im assuming there is a backing nut that has come loose or off from the inside.
How do I reconnect the inside backing nut
To the loose outside bolt
Is there a lot of work to get at the back of this bolt?
Please help