Getting under their skins.

• Position: GoodMark Foods Inc.'s Slim Jim Central plant

Preparing for a trip through GoodMark's Gamer plant, you feel like an Apollo astronaut prepping for flight. All jewelry comes off. No watches. No hair below the earlobes. You put on a white lab coat. Then a hairnet and hard hat.

This is Slim Jim Central. The 277,000-square-foot plant, tucked in trees a quarter mile off Interstate 40 on Jones Sausage Road, chums out 95% of the brand - 290,000 pounds a week. That's 200,000 Slim Jims every hour.

Meat processing isn't a pretty business. More than 50 million pounds of meat pass through the plant each year - 65% of it beef, the rest chicken and pork. The pork ends up in Jesse Jones sausages and bologna. Slim Jims use chicken, most of it local, and beef, from as far as Nicaragua and New Zealand, depending on the going rate.

The recipe is locked in a fireproof vault at headquarters, and only three or four folks in the plant know the exact ingredients. What goes into a Slim Jim is the subject of a lot of idle curiosity. Steak may be 10% of the cow, CFO Paul Brunswick says, but "there's nothing wrong with the rest." GoodMark draws the line at organs and hooves.

This day, there are 60-pound boxes of frozen head beef ("trimmings from around the head," plant manager Wade Wannamaker explains) from IBP Inc. in Dakota City, Neb., rolling through the steel receiving doors. The meat is thawed in industrial microwaves.

In preblending, a computer shoots precise amount of meat down a or belt to be ground into pulp. On way, it passes through metal Some Western ranchers favor shotguns for herding cattle, and GoodMark wants no kid chomping down on stray lead.

After grinding, the chicken looks like damp, gluey sawdust. The beef is a brown sludge identified by its mix number. It sits around in half-ton stainless-steel tubs - "925:G pureed beef shanks," perhaps destined for Giant Slim greatness. A sign on the wall reads, "Think Quality."

The meat moves on to the blenders. In 12-foot-high open-top vats, huge...