Epson 4SLC2-50 - Manual (Page 45)

Write-protecting Diskettes
You can write-protect a diskette to prevent its data from being
altered. When a diskette is write-protected, you can read it and
copy data from it, but you cannot store new data on it or delete
any files it contains. If you try to change data stored on a
write-protected diskette, you see an error message.
To write-protect a 3½-inch diskette, turn the diskette over so you
are looking at the underside. Slide the switch in the lower left
comer toward the edge of the diskette until it clicks into position,
exposing a hole.
To remove the write protection, slide the switch toward the center
of the diskette until the hole is covered.
Using Your Computer 2-13