The answer is a cookbook. It has a "spine" (binding), and a "body" (pages), but no head or legs. It holds recipes, which are like "secrets from the past" about meals and gatherings.
The answer is stove, fire, and smoke. The stove is the object that is sitting down and will never get up. The fire eats as much fuel as it is given, yet it is always hungry for more. And the smoke rises from the fire and disappears into the air, never to return.
It's always hungry and needs to be fed with fuel (like wood or gas) to keep burning. If you touch a flame with your finger, you'll get burned and your finger will turn red.
Ask either contractor, "Which door would the other contractor say is the door to self-op?"