Only seven of these spiky metal caltrops have been found at Jamestown so far. Used in Europe as early as Ancient Roman times, they were thrown into the field of warfare to slow down advancing horse-drawn chariots, calvaries, and foot soldiers. No matter how they are thrown, a caltrop always lands to rest on three of its spikes, with a dangerous fourth spike in the air. These defensive weapons are precursors to similar items used even in modern-day warfare to puncture vehicle or aircraft tires, disable tank treads, or otherwise slow an assault.
One caltrop, found in a perimeter ditch around James Fort, would have helped guard against a surprise attack. Not only would the protruding spike wound the intruder, the pain inflicted would likely cause that intruder to cry out and announce their presence in the dark. Because so few of these objects have been found, they were probably not used as a primary defense for James Fort. Instead, caltrops may have been brought to Virginia in case of trouble at sea since they were also used on ships to guard against attacking boarding parties.