Crossing

"Laying down tricks in the form of wavy lines, circles, and cross-marks on the ground is an old African custom that came to America in slavery times. Spitting into the design activates it, and when the enemy walks over the powder, he or she is said to be "poisoned through the feet," bringing on a Jinx and creating Crossed Conditions that result in all-around bad luck and long-lasting illness."

The ingredients in Crossing formulas may include Salt, Cayenne Pepper, Black Pepper, Sulphur, Graveyard Dirt, crossroads dirt, ashes, crushed snail shells, spider webs, crushed insects, unravelled hemp rope, gum arabic, rattlesnake dust (powdered shed skin of a rattlesnake), black hen's eggs, and other herbs and essences

Crossing is a strongly African concept in hoodoo, a sub-set of the tradition known as direct foot-track magic, whereby one can affect another by

gathering up their foot-print dirt and working with it,
causing them to step upon or walk across something evil, such as Crossing Powder or Hot Foot Powder,
causing them to contact with their foot something that will bend them to your will (e.g. Court Case Root or Essence of Bend-Over Powder),
placing something in their shoe or sock to harm them, such as Goofer Dust,
collecting one of their socks and washing it in Crossing Crystals or
working candle-magic with it. for example, by burning a glass-encased DUME (Death Unto My Enemies) or Black List candle dressed with a combination of Crossing Oil and magic herbs for harming.

Cross-marks and "wavy snake lines" intended to hurt an enemy can be laid down with small stones, inscribed in the dust with a sharp stick, or drawn with chalk or sprinkled Crossing Powder on a sidewalk or street. The marks are placed in the foot path of the victim and activated by spitting into them while cursing the one for whom they are laid.

What happens to innocent people who walk over such marks is a matter of debate. Some folks will tell you that the cross-mark only affects the one it was put down for -- but almost as many people will tell you to never walk across such a mess when you see it, because you just might get crossed or "hurt through your feet" anyway.

http://www.luckymojo.com/crossing.html