A caltrop is a spiked device used historically as a weapon to hinder the movement of enemy troops and cavalry. It consists of four sharp spikes arranged in such a way that at least one spike always points upward, making it effective for puncturing tires or hooves. Caltrops were commonly used in warfare to create obstacles on battlefields. In modern times, caltrops are often used by law enforcement and military personnel to stop vehicles during high-speed chases. They can also be found in some security systems to deter intruders. The design of caltrops has remained largely unchanged due to their effectiveness in creating barriers.