This is a pad Feeler gauge. They are made of many different materials (depending on your preference), but we were taught to use a wooden dowel and a narrow strip of mylar. Mylar is used because you can purchase it in very precise thicknesses. This strip of mylar is 0.001" thick and is about 1mm wide.

This is how a feeler gauge is used. You place the strip of mylar under the pad cup, close the key very VERY lightly and lift the gauge. If the pad is making contact with the tonehole, you will feel what we call 'drag.' Basically, this means you feel resistance when you pull it. This is actually a skill that takes some time to develop because you have to establish consistency of technique, and a touch that is far lighter than that of any professional player.

Once you find a place where the feeler gauge is not getting any 'drag' you mark it with a pen. At this point it helps to think of the key like a clock face. The key arm will always be 12 O'Clock. To level a pad like this you must heat the Key Cup to melt the glue inside.

Here you can see how we were taught to heat the key cup. Some people use alcohol lamps that generate a very low temperature flame. We use acetylene torches with very low pressure in the lines. The amount of fuel being pumped through the torch is very important. These torches have the potential to melt metal instruments if you don't control them. Here you can see that I merely touch the side of the flame to the back of the key cup very briefly, then close the key a few times, and then hold it gingerly in place. This effectively floats the pad in a bed of glue and uses the tonehole as a leveling device.

This class was structured quite differently than our brass class simply because we are practicing most of the techniques as we are overhauling the instruments.