wards vs summer tracking

"That's interesting," Thomas said, "but that's not what I was asking about."
"Oh, right," I said. I pointed at the catnip bag. "The leaf 's in there."
"Isn't that just going to draw Summer's goons here?"
I let out a nasty laugh. "No. They can't see it through the wards around the lab."
"Then why the big rubber band?"
"I linked Summer's beacon spell to the matrix around Little Chicago. Every time the leaf gets within a foot of the model, my spell transfers the beacon's signal to the corresponding location in the city."


Small Favor Chapter 10, Page 76