On 10/31/21 10:07 PM, Ali via cctalk wrote:
  "Computers that used the floppy index hole also
required two additional
 openings in the floppy case to allow the drive to access when the disk was
 upside down. However, it was a difficult and risky operation for the
 integrity of the support. To facilitate this intervention, there were "guide
 masks" which allowed to accurately trace the position where the hole was to
 be made. These tools included the "Berkeley Microcomputer Flip-Jig" which
 was available for both 8 "and 5" 1/4 discs." 
Interesting.   When I was using 8" disks early on, the only ones
available were single-sided.   However, several manufacturers produced
"flippies' with labels on both sides.   I still have several such
examples in my stash.
You'd think that a simple cardboard template would serve to allow users
to mark additional hole locations, however.
--Chuck