I’m sure there are more precise, and sturdier ways to attach a perforating base to a tympan, but I can find no product better than, you guessed it, 3M Post-it tape.
I am no fan of changing my tympan for every job. It is time consuming, and wasteful. I hope to get through my printing career without buying another roll of tympan paper. So most of the tips on this site will revolve around cutting corners, saving time, being cheap, and NOT replacing tympans. (Though there is a tip coming for that.)
I use the flat perf base, Post-it tape has just the right amount of tack to hold down a perf base. It’s repositionable, and it doesn’t tear up the tympan when it’s removed.
Once the perforating rule is locked up and positioned for the run, I will mark its location on the tympan. If I have set the packing correctly, it shouldn’t leave a mark on the tympan when pulling an impression. Two pieces of Post-it tape on each end, raised slightly with a piece of cardstock is enough to find the location of the perf.
Then a couple pencil marks on the tympan before removing the temporary locators.
Connect the marks with a line, extending past each end of the base.
I have found the tape on top of the base also gives the perforater a little more bite, and punches through the paper with less pressure, and hopefully extends the life and sharpness of the perforator.