placard

He lowered his hand slowly, his expression resolved. Then he took a step back, pursed his lips, looked at me, and shook his head. After that, he moved briskly, opening a storage cabinet and taking out a small, efficient toolbox. A moment of effort and he’d put a couple of screws in the back of the sign, connected by a strand of wire.
“What is it?” Murphy asked as he worked.
“The placard from the Cross,” I said. “The one that said, ‘Here is the King of the Jews.’”
Her golden eyebrows went up. “From the vault?”
“Yeah,” I said.
“What does it do?”
“It’s embodied intercession. . . . It focuses energy on an individual,” I said. “Something about pouring out the accumulated sins of humanity onto Christ, maybe. Hang it up and it puts up a kind of threshold that will hold off just about anything supernatural, as long as the property’s rightful owner is alive.”
Mac took a small folding knife out of his pocket, opened it, and pricked his thumb. A drop of blood welled.
“So everyone here will be safe,” Karrin said.
Mac hesitated for only an instant. Then he took a deep breath and pressed his thumb against the back of the placard, smearing his blood there.
“Anything that wants to get to them will have to go through Mac first,” I clarified quietly.
Mac took out a nail and a hammer; then he tucked the placard under one arm and walked out with them. A moment later, we could hear him using the hammer as he hung up the sign.

Battle Ground Chapter 3, Page 24-25