In Ezekiel 15, what is the wood of the vine said to be good for?

Answer: Fuel for the fire

Vine wood cannot be made into anything, not even a peg to hang utensils on; it is cast into the fire for fuel—a picture of Jerusalem's people.

“No, it is cast into the fire for fuel. The fire devours both ends, and the middle is charred. Can it be useful for anything?”— Ezekiel 15:4 (BSB)