a nail gun has a free end 19 a and central potion of a trigger arm 19 positioned within a trigger 11 , on an upper end 12 a of a safety portion 12 and at a plunger 17 , respectively . when the trigger 11 is pivoted on its pivot end 16 , pivoting movement of the trigger 11 moves a pivot end 18 of the trigger arm 19 to press the central portion of the trigger arm 19 into contact with the plunger 17 and , with the plunger 17 serving as a fulcrum , to press the free end 19 a downward against the upper end 12 a of the safety portion 12 . if downward movement of the safety portion 12 is obstructed when the trigger 11 is pivoted , the upper end 12 a contacted by the free end 19 a of the trigger arm 19 serves as a fulcrum around which the trigger arm 19 pivots with movement of the trigger 11 , whereupon the central portion of the trigger arm 19 presses the plunger 17 inward so that an activation switch 10 activates a blade 7 to eject a nail through a nose piece 5 .