'Cadweld' is a brand name of an exothermic welding system. Basically, a graphite mold for the specific type of weld you are doing, a clamping device to hold the mold halves together. You install the mold over the weld you want to do, clamp it, insert a metal disc in base of powder chamber, pour in a patented measured unit of weld powder/compound, insert ignitor, install filter and mold top cover. Step back a safe distance, activate ignitor, powder ignites heats compound to melting point, disc melts away, compound falls onto material that you want to weld, and that's it.
Next step is wait for mold to cool & remove; check & clean weld.
Keep in mind 'wait for cooldown'!!!
The Cadweld system is part of Erico Corpwww.erico.com
They have a fairly current training video, CD/DVD. You should be able to request a copy from the website.