These are known by a few different names (Billy, Thermette, BackCountry Boiler, storm kettle, volcano kettle, Kelly Kettle, or Bush kettle) depending on your locale. They all work on basically the same principle of a water jacket around a wood fire to boil the water.
The commercially available varieties are quite expensive however, and when I spotted an old broken electric jug in my favorite local dumpster, I had to have a go at making one.
The process I used involves fabricating a cone out of the same material as the donor jug, and welding it in place, making a donut of sorts.
I've seen copper, aluminum, and stainless wood-fired kettles, this one is stainless steel, and to my knowledge is the first of its kind with transparent viewing windows in the sides.
The first thing I had to do was get rid of all the extra bits I didn't need. Fortunately I had the 3 point driver bit I needed for the tamperproof screws. With the bottom & the handle off, all I had to do away with was the heater element. Ye olde multipurpose chisel made short work of that, a few good whacks and it popped right off.