The most popular and most devious ways to protect floppies on the Apple ][ were more or less all based on timing bits (including the most famous protection of a

The most popular and most devious ways to protect floppies on the Apple ][ were more or less all based on timing bits (including the most famous protection of all, the E7 slipstream). These timing bits were necessary on the disks for the reading head to be able to tell 1's from 0's, but copiers did not have the ability to maintain them, so copies were often desynchronized. AppleSauce is the only device that can successfully preserve timing bits, hence allowing protected disks to be copied. Source: I crack Apple ][ programs for fun.