OTF (Out-the-front) knives are switchblade automatic knives, often abbreviated as OTF knives are called telescoping or sliding knives. Some people refer to them as automatic knives, although these two terms are not interchangeable because automatic knives can also be side opening. Forty out of the 50 states have legalized OTF knives, which is a significantly higher number than a few years ago, due to the work of knife rights groups.
There are two types of OTF knives: single action and double action. This distinction refers to the mechanism inside the knife which controls the blade’s motion. Single action knives will fire automatically but need to be retracted manually. The Microtech Halo is an example of a single action knife. A double action knife allows the knife to be deployed and retracted by using a thumb slider or button on the handle. Members of the military, law enforcement officials and first responders use double action knives because of their ease of use in an emergency or extreme situation.