Heck Lugnut, we used a piece of plywood for a lid and just popped a few holes into the bottom with a pick ax for vent holes then poured the coals into the bottom of barrels for years before they burnt out. We also just notched the top of the drum and spanned the drum with a single piece of re-bar and used meat hooks to hang our meat in the drums.
That's what is so awesome about these things, they all cook pretty close to the same. It's just a matter of how simple or fancy you want to make them.
my next usd will have a coal door, I'm not worried about it being air tight at all. I can hold 285* for close to 30 hours with one basket of coal with 3 of my lower vents open . Hell it will keep hot coals for 3 days if I shut down the vents.
Yeah I know then why do I need a coal door ? because I have a really bad back and don't like hoisting the basket over the top of the drum.