Caltrops are often seen in Ninja movies or in the imagination of Martial Arts enthusiasts. An object that is so simple but yet effective for thousands of years.

It started with a simple idea…how can I slow down or stop someone chasing me? You create a small metal object that when thrown, one sharp spike always sticks up.

You throw a lot of these in a way that the person chasing you can not see, then you will slow him down or stop him for good as the sharp point will be stepped causing pain.

Even in today’s world you can see caltrops being used on a daily basis by law enforcement. They use modern versions of this philosophy to stop vehicle by popping the tires using spike strips.