Yes. But not knowing how to measure them and not being able to measure them are two different things. Sigils are a language. Even if we know where they gain their power, measuring that source is another matter.

[It's a pity Professor Grouse wasn't here, or at least that Anton hadn't spoken to him more deeply. But Anton hadn't needed to hear much theory about how sigils worked--as long as they worked, and he knew how to use them.]

They do. The nuance of their input can occasionally be difficult, but if you require a practical example the Midnight Hotel is built of them.