I wanted a more modular version of a fire wall so I can build the wall the way I wanted, so I split up the original fire and made some small modifications to make it a little nicer as a repeatable wall tile.
The main fire wall piece should take up 2 squares on a standard battle map (about 2 inches). You can just print multiples to build the length of wall you want.
I've included the cropped pieces from either end that can be printed if you want to make the end of the fire wall taper off to look a bit nicer visually on your battle map. They are not required to print for use if you don't want it.