Carl's first-generation thermobaric bomb, wheeled and Fear-laden, used on the sixth floor.
Before the Waffle Maker, Carl built a bomb called Just Wait Until Your Daddy Gets Home and used it on the sixth floor. It packed roughly the same punch as its successor and additionally applied Fear, but it was so large it had to have wheels.
The Waffle Maker is its refinement: the same yield minus the Fear component, packaged self-contained in a device the size of a thermos, limited in production only by how much of a pain the explosive dust is to make.
A bomb so large it required wheels to move.
The bulky prototype behind Carl's thermos-sized thermobaric bomb.
Also appears in books you've already read — spoiler-safe to their endings: