Easy to make and 1 way so the player camera can’t go trough and can’t see inside even a small bit.
STEPS
STEP 1
You need to make a normal brick and change the transparency to 0.02
Duplicate that part
Should look like this
And the properties for both of them
STEP 2
Then you make 1 brick and make the transparency to your liking and the material must be glass
STEP 3 (OPTIONAL)
You can make a frame for the one way glass EXAMPLE:
STEP 4 (OPTIONAL)
Place the glass into the frame (if u made one)
STEP 5
Place the 2 0.02 transparency bricks into the glass, not too much that it pokes out of the other end and if u still can see trough you can duplicate the 0.02 bricks until you cant.
END RESULT
I hope this helps.