The touch-n-flow applicator is a thin glass tube with a steel needle at the end that one uses to weld parts together with the included Plast-I-Weld, or any other liquid glue (I have had success with the Testors glue that comes in the glass bottle, as well). There's a bit of a learning curve, especially if you buy the tool without the filler bottle, but once you get the hang of it, this thing makes life much easier. I'm basically a huge klutz, and I normally make a big mess with polystyrene cement. The touch-n-flow allows me to put the glue just along the seam between the two parts I'm joining (capillary action draws the liquid in, and it's easy to control), and by squeezing the parts together, the melted plastic beads up along the seam. Use the back of a knife blade to scrape the bead away, and the seam is gone, without using putty or other filler. I'm also pretty sure you could leave the bead of melted plastic along the seam line to simulate a welded join. The only complaint I have is that the tool is fairly fragile-it's made out of glass after all, and the needle can bend if you're not gentle with it.