Original sentence: On the other hand, the use of index-sync meant that in order to turn a floppy disk into a "flippy", it was necessary not only to cut a second write-enable notch, but also to punch a second index hole window in the jacket (at great risk to the disk inside).One could also purchase factory-made "flippies", or use the back side for Apple systems (as some software publishers of the era did)
Edited sentence: On the other hand, the use of index-sync meant that in order to turn a double-sided disk into a "flippy", it was necessary not only to cut a second write-enable notch, but also to punch a second index hole window in the jacket (at great risk to the disk inside).One could also purchase factory-made "flippies", or format the back side for Apple systems (as some software publishers of the era did)