you will sometimes have a problem to scan your negatives with your slide carrier:
*you may want to scan them with their borders.
*maybe, your negatives are not fitting in your slide carrier
*or like me, you don't like the 6*6 carrier, who can't get the negative flat !!
Step 1: First idea
but strange pattern like that could appears ...
newton ring ...
you negative mustn't touch the window's scanner...
it would be ok for 35mm negative if you put them upside down
not perfect but it's enough for most case.
but this don't work for 120 negative, they don't stay flat ...
Step 2: The clothespin hack
*they will handle the negative 1mm above the window's scanner.
*they are enough heavy to get the negative flat.