How do you make black line with the edge of your nails?

Cashiers do it all the time at clothing stores on the receipt. They use the sides of their nails to make a black line the peice of paper. How do you do it? Thanks!!!How do you make black line with the edge of your nails?
You can do that on thermal paper. It's used in receipts and credit card slips. It reacts to heat, including heat generated by friction of fingernail. I experimented in your behalf, and voila, there's the black line.How do you make black line with the edge of your nails?
How? You just press your nail and run it along the paper. We do it because sometimes there isn't a pen on hand and it's just easier. The paper is so thin that it's easily marked.
no idea.





http://answers.yahoo.com/question/index;_ylt=AgkYfhxc6uNroe4H.b25dnPsy6IX;_ylv=3?qid=20090408221239AANm0gt
Im positive it must be the paper!





Like..when something hard hits it it turns black. Maybe its to save ink?





I have NO idea! Hope that helpped
really u gurls r !!!! Sorry d't know..i'll try to find..meanwhile lemme collect some points...hehehe..:)