Fold In or Out on Score Lines
There are many opinions on the best way to fold on the score lines, and I put them to the test.
Here are two pieces of pink cardstock with a score line down the center.

I’ll start with the piece on the right and fold in on the score line, so the dent from the score line is inside the card.

With the card on the left, I flip it over and fold it in half so the indent becomes the outer spine of the card.

The results are very similar, but there is a slight difference.
That folded paper has a bit of fraying along the spine of the fold. There isn’t a lot, but I think the fold is a bit nicer when folding in.

No matter what method you are using to create the score line, I always recommend using a bone folder along the fold.
Applying pressure over the fold will provide a nice, clean fold and help it lie flat.
