Bone folders are the best friend of anyone using art paper.
When I began learning book and paper conservation, it was first tool they gave me.
When I'm printing, collaging, making cards, bookbinding, glueing, assembling custom keepsake or book boxes, I always have my bone folder close by. It's an extension of my hand.
One thing they enable you to do is to make a sharp fold for cards, or the endpapers of a book for example.
Scoring a line before you fold it weakens the fibres at that point and compresses them so the paper folds naturally.
Press it down with the smooth surface of the bone folder, and you’ll have a perfect, crispy, professional edge.
Keep your bone folder handy to help you move your paper around, so you're using your bare hands as little as possible and avoid puckering or creasing. Use your bone folder to gently lift the paper!