There are two types of triggers on a nail gun. Sequential triggers will drive a nail whenever the trip and the trigger are depressed at the same time. This method is preferred by the contractors because is faster than the other trigger system. If you keep holding the trigger and bumping the trip against the work to be nailed, a nail will be driven each time trip bumps on the surface. There is a high risk of falling or bumping the trip against other things than the work surface and getting injured.
The other type, the safest, is the contact trigger. This one will not drive a nail even when the trigger is pulled against any surface. In order to drive a nail, the operator must first depress the trip on the surface and then pull the trigger. Every time you want a nail to be driven you must do the same action, this way it prevents accidents.
