"A circle like this with the line on the inside and dashes on the outside acts, absent any exculpatory logic, like a roach hotel for dumb smart cars. (Of course, it’s just a regular car he drives into it for demonstration purposes. It would take too long to catch a real one.)
"It’s no coincidence that the trap is drawn with salt (the medium is listed as “salt ritual”); the idea of using salt or ash to create summoning or binding symbols for spirits and demons is an extremely old one. Knowing the words of command or secret workings of these mysterious beings allowed one power over them."