See, I noticed something interesting in your hotel room. Something tucked above the door. An herb. Devil's shoestring? Well, there's only one use for that. Holding hellhounds at bay.
Bela uses it to try and protect herself from hellhounds when her crossroads deal is up. When Dean holds her at gunpoint, he notices a branch of devil's shoestring tucked above the door frame. It was this discovery that helped him realize that Bela made a deal.
Devil's shoestring, along with a cat skull and grains of paradise seed, is a part of a spell to summon Veritas, the goddess of truth.
- Devil's shoestring is a common name for different types of viburnum, a plant that grows in North America, belonging to the honeysuckle family. Devil's shoestring is used in hoodoo. The plant produces long vines which are used for protection to "trip up the Devil" so he can't get in the house. They can be driven into the ground near the front door or left on the door lintel.