A Piranha (also called Fish Bone 2.0) is a great tool that enables you to secure paracord up to 4 mm thick without tying knots. The basic principle of all versions is the same: you place the end of your paracord on your Piranha and wrap it around it. Because of friction your paracord will be properly secured. The other side is wrapped around the head of the fish twice. A Piranha is a little stronger and thicker than a Fish Bone.