Devil's Trident

While not named on Supernatural, this symbol associated with Hell appears on a number of occasions. The trident or pitchfork, appears to be both symbolic and a practical - it can prevent a demon from de-possessing its human meatsuit, as well as act as a type of warding sigil.

Episodes

5.20 The Devil You Know

Having fled his palatial home, Crowley has taken up residence in a ruined house, that has tridents painted on the walls and windows. When Crowley and Dean capture Brady in order to ascertain Pestilence's location, Crowley carves a trident into Brady's chest, telling Dean it will prevent the demon leaving the body.

Crowley: This bit of carving will tie our friend here down. No zapping off, no smoking out - locked in the meatsuit.

Tridents graffitied over Crowley's house.

Tridents graffitied over Crowley's house.

A trident carved into Brady's chest.

5.22 Swan Song

When Sam and Dean find Lucifer in Detroit in an abandoned building, he doodles a trident into a frosty window.

Lucifer doodling a trident in the frost.

6.20 The Man Who Would Be King

When Crowley is bargaining with Castiel in Hell, they pass a portrait of Crowley wearing a Nazi-style uniform which bears a trident insignia on a patch on the left sleeve.

Crowley wearing the trident insignia.

6.21 Let It Bleed

A variation on the trident symbol appears on the front door of Eleanor Visyak's warded safe house.

The warding on Eleanor Visyak's safe house.

6.22 The Man Who Knew Too Much

The trident appears among the various warding sigils in Bobby's panic room.

The trident in Bobby Singer's panic room.

8.10 Torn and Frayed

The trident appears among other warding sigils in the abandoned factory where Crowley is torturing the angel Samandiriel.

The warding in Crowley's hide out.

8.17 Goodbye Stranger

Sam and Meg paint warding sigils on the warehouse housing one of Lucifer's Crypts.

Warding sigils painted on a warehouse.

10.03 Soul Survivor

The drink Dean orders Crowley has a Trident in it.