You put it between two pieces of paper, then you write on the top one and it creates as copy on the bottom one.

你将它放在两张纸之间，然后你在上面那张纸上写字，下面那张纸上就会复印下来。

youdao

You put it between two pieces of paper, then you write on the top one and it creates as copy on the bottom one.

你将它放在两张纸之间，然后你在上面那张纸上写字，下面那张纸上就会复印下来。

youdao