I used some of my wife's picture hanger wire, thin and pliable. The outside of the forge will not melt aluminum, well it didn't on mine which is a two bricker. I used 1" pieces of half inch aluminum angle on the edges to prevent the wire from cutting into the soft fire brick. I found the wire binds on the edges and didn't want to slide as I took up the tension on the wire. I resolved that by using two pieces and twist tied them. Two wraps around the thickness and two wraps around the length. You will get expansion and contraction cracks in the soft firebrick. I have a crack that runs completely around the two bricker where the two faces meet. I covered the exterior with refractory mortar to protect the fire brick from wear and tear. Interior chamber has a skim coat of refractory mortar coated with ITC-100. It rests on four soft firebrick when fired up.
Used it for four years till I built a freon tank forge last summer.