I found another use for the needle gun!
In 1979 I was in the US Navy, stationed aboard a ship that was being refitted. We were in a drydock, and had to do construction type tasks all day. One day my job was to go way down into the lower part of the ship into a powder magazine, and prepare the metal walls to be painted by chipping off all of the old paint. The tool that I used was called a 'needle gun'. It was powered by compressed air. The idea was to hold the end with the 'needles' (several dozen steel rods that resembled welding rods)against the wall and press on the trigger, this made the needles move back and forth rapidly and they literally chewed the paint off of the wall. The steel rod ends were not sharp, but were smooth and rounded with use. Using this tool for any length of time made my arms and hands tingle from the extremely intense vibration. I was all by myself in this little room, and I soon had an idea. I placed the end of the rods on the crotch of my dungarees over my penis head, and lightly squeezed the lever that fed the compresssed air. It felt amazingly good, the vibes soon making me hard. I adjusted my dick so that it was sticking straight down my leg, still inside my pants. I played the needles up and down the entire length, squeezing the air trigger a little harder, but of course never reaching full paint-destroying intensity. What I did reach was a mighty orgasm, squirting spooge onto the inside of my pants leg leaving a large moist spot. Fortunately the navy pants were dark blue and I had time for it to dry, also the spot was nearly to my knee (I am well endowed) so it would not seem to be semen-related. The Navy, not just a job, it's an adventure!