The problem with those master cylinder screws is that
they get all hosed up if you use a regular phillips on them.
The right kind of screwdriver (JIS) is in the tool kit. I have this
50yo lefty-loosey-righty-tighty ratcheting screwdriver, it has
a correct bit.

I've been using my lefty-loosey screwdriver on these
screws for 15 years:

I found these ones to be perfect replacements for the
rear master cylinder screws:

-Mike