鉄菱
Literally "iron thistle," tetsubishi were caltrops used by the ninja to deter pursuit. These small, extremely sharp metal objects could be easily carried in a pouch or a bamboo tube and scatterd along paths, walls, or halls. The took a variety of shapes and sizes, one of the most common being a tetrahedral design with four spikes joined so that no matter how the tetsubishi landed, one of the spikes would be pointing upward.