|I use fax rolls for my John Smith organ music, and have a foot
switch controlling a repeat punching timer for cutting 'slots' easily. It
works fine, but occasionally my toe twitches and I punch an unwanted hole.
Trying to poke a pen under the master to mark the fax sheet is a pain, as
it is extremely fiddly to separate the layers.
I have an 'instant heat' soldering iron ready when punching. I can
press the button for a few seconds (too long and the effect would be too
severe) and touch the tip on the master beside any offending holes. The heat
makes the fax paper turn black, leaving the unwanted holes marked for covering
with some of the tiny round sticky labels one can buy at the stationers.
The same effect could be produced with a normal soldering iron, but it would
have to be switched on all the time to be ready for use, and I think that
besides twitchy toes, I could end up with burned fingers!