Thanks again for your help about bricks under the furnace.
What do you call those things in the main ductwork close to the
furnace that are mostly vinyl, 6 inches high, that clamp on to the
ducts at each end?
There's a band about an inch wide at each end. One end clamps on a
short duct from the furnace, and the other end clamps on the outgoing
or incoming duct from the house.
In the middle of that is a piece of grey vinyl about 4 inches wide,
following the perimeter of the duct it's attached to.
I need to replace mine but I don't know what they are called.
Do you know if they are there to keep vibration noise from getting
into the ducts, or to make up for minor misalignment between the
furnace and the duct?