Disk notcher
Updated: 04/26/2017 by Computer Hope
A disk notcher or disk punch is a device that converts a single-sided 5¼" floppy disk to a double-sided floppy disk by adding a write-enable notch to the disk. The addition of the notch allowed data to be written to the other side.
If the floppy disk drive used a start of track index, an additional pair of notches had to be added to the floppy disk jacket. The image is an example of a disk notching tool.