For you Folks with downdraft Gassification boilers, you call them Nozzles. With the Jetstream, they are called Tunnels. Made three forms as I was not sure how far the 55lb bag would go. Turned out it made 2 tunnels. Two completed tunnels. The forms were made so it would come apart easily. Stainless steel needles are the re-bar. The PDF is for the refractory that was used.
http://www.newhorizonstore.com/ Is a source for both refractory and the needles. We bought our refractory and needles locally which represented a 2 day round trip to and from Vancouver, BC.