What does the 3rd lock button do?

Hi,
There are 3 buttons in the Layer operator properties Lock section. 1st locks alpha, 2nd locks move of layer (found it in another post), how about the remaining one?
Thank you.
There are 3 buttons in the Layer operator properties Lock section. 1st locks alpha, 2nd locks move of layer (found it in another post), how about the remaining one?
Thank you.