 Locksmith copied Apple II disks by taking advantage of the fact that these sync fields between sectors almost always consisted of a long string of FF (hex - all '1' bits) bytes.It found the longest string of FFs, which usually occurred between the last and first sectors on each track, and began writing the track in the middle of that; also it assumed that any long string of FF bytes was a sync sequence and introduced the necessary short pauses after writing each of them to the copy.Ironically, Locksmith would not copy itself.