Canon EOS REBEL T6i Instruction Manual page 303

3 Protecting All Images in a Folder or on a Card
You can protect all the images in a folder or on a card at once.
If you format the card (p.59), the protected images will also be erased.
Movies can also be protected.

Once an image is protected, it cannot be erased by the camera's erase

function. To erase a protected image, you must first cancel the
protection.
If you erase all the images (p.305), only the protected images will

remain. This is convenient when you want to erase unnecessary images
all at once.
When you select [All images in folder]
or [All images on card] in [31:
Protect images], all the images in the
folder or on the card will be protected.
To cancel the image protection, select
[Unprotect all images in folder] or
[Unprotect all images on card].
K Protecting Images
303