Toshiba T100 Manual page 59

WRITE-PROTECTING FLOPPY DISKS
Occasionally, you will want to protect the information on
your disk so that the data on it may not be accidentally
changed. You may accomplish this by placing a small
piece of silver paper over the "write-protection" slot as
indicated in the illustration at left. Your disk becomes
"read only." To write on the disk again, simply remove
the silver paper.
You should now write-protect both of your system disks
(T-DISK BASIC and CP/M).