This is a tool that should be completely obsolete. The only reason a shop should have one, should be to tweak old brakes. Old as in the 80's. I should not be using this on brand new caliper brakes. Unfortunately it is a tool that I use on a regular basis on new, out of the box caliper brakes from that brand that makes so many OEM products, Tektro. I'm not sure why, but they just can't quite seem to get the arms straight...
As a side note I could not find this tool offered from Park any more (granted I searched for about 32 seconds but that is beside the point). So I guess I should just be happy I have one at my disposal for those times when they are actually needed.
For those of you unfamiliar with this tool, it is a Park BT3. It is used to "tweak" the arms on a caliper brake to get the pads to line up or toe the way you want. With modern brakes the arms are usually formed close enough to straight that with the conical washers now used you can get the pads to line up. Unfortunately, there are still some cheap ass brakes out there that just don't quite make the cut.
You can get a visual here, http://www.amazon.co.uk/Park-Tools-Brake-Toe-Tool/dp/B000NOO4O6.
I guess I should thank God that I work in a shop that has been around long enough to have old tools that are no longer available.