So I think you are referring to the notch on the side of the disk. If it was present the disk was writable, if not then read only.
It was common to write-protect a disk using a small sticky label, folded over the notch. From memory, disks came with these labels.
We also found out you could add a notch on the other side, and use the disk upside down (ie as a second disk) thus doubling the storage value of each disk. All magazine materials explained why this was a bad idea, lead to data corruption etc, but it worked well and so we ignored the warnings.
This became so popular that I remember owning a punch literally made for this exact purpose. It positioned the disk in the right place and cut a perfect square notch. So this practice was wide-spread enough that someone actually designed and produced a tool to do it.
But yeah, in the early days, we used scissors (very carefully).
Any chance you still have the punch? I got a box of double sided disks that were intended for a double sided drive, so only had notches on one side... Would be lovely to notch 100 disks the easy way.
There are still some stores that sell these "floppy disk notchers" [1] if you're feeling really nostalgic for authentic vintage units, and occasionally they'll pop up on the usual auction sites. Or you can 3D print yourself one these days [2]. I was too poor to get a real notcher, so made do with an X-acto knife and a cardboard template I would create over and over. By the time I could afford a notcher, the muscle memory was etched into my fingers and hands, and I never bothered to get one.
It was common to write-protect a disk using a small sticky label, folded over the notch. From memory, disks came with these labels.
We also found out you could add a notch on the other side, and use the disk upside down (ie as a second disk) thus doubling the storage value of each disk. All magazine materials explained why this was a bad idea, lead to data corruption etc, but it worked well and so we ignored the warnings.
This became so popular that I remember owning a punch literally made for this exact purpose. It positioned the disk in the right place and cut a perfect square notch. So this practice was wide-spread enough that someone actually designed and produced a tool to do it.
But yeah, in the early days, we used scissors (very carefully).