Rendering lard was just always called makin cracklins. All the fatty pieces and the skin were cut fairly small and crisscrossed like a Tic tac toe board to cause efficent cooking.
You start in a big cast iron pot, dumb in the all the scraps, a little water to get ya started (It will evaporate), and pull to the paper covered table when its done to wick away excess oils. You then spirnkle with spice.
You start pulling the cracklins when you see the first whisps of blue smoke comming off the pot. never thought about that but I guess that is thin blue smoke.
Whats left in the pot is covered and cooled. And it doesn't taste like that store bought purified stuff.
Someone here showed in a Q-View, baking off the fatty pieces in the oven, then said they could actually later deep fry the pieces making a cracklin. I have not tryed it though. Good cracklins are readily available in all the stores here so we don't make 'em too much anymore.
Throw the butts away, make sure and cook that fat.....LOL