gun of the present invention for opening and closing the passage of high pressure air to the needle carrier and the piston cylinder assembly as hereinafter described the housing 12 is a substantially inverted l shaped member having a hollow 20 at the top and a tapered open top channel 22 opening into the hollow and extending out the leg 24 of the l shaped housing 12 the channel being deeper between the hollow and a pair of upright ledges 26 that at the free end of the leg 24 for reasons which will become apparent the wall forming the hollow is open at 28 oppositely to the channel over an angle of approximately 90 degrees the housing is sealed at the top intermediate the hollow and the interior of the handle and to this end a tight fitting disk shaped plug 30 having an upstanding pin 32 may be inserted into the top of the housing the pin extending upwardly into the hollow it is visualized that rather than a separate plug 30 the housing would have a floor formed between the hollow and the handle 14 such as at 31 and the pin 32 would then be secured to the floor positioned about the top portion of the pin 32.