A small leak can mean big trouble in a filling line. For liquids, clean up may demand that you stop production. And in pharmaceuticals, where you have to account for labels and product, leaks are a very expensive occurrence. The process is straightforward: a hose drops down and seals against the neck of the bottle. Air blows in. If air escapes, perhaps through a hole or a "short shot" (misshaped neck), the bottle gets kicked off the line.