1. The signature may be forged as an IOU or IOU: a. The signature is in the middle of the blank paper (not necessarily in the middle), and there is a blank position on it where the IOU can be forged. B, the signature is at the bottom of the blank paper, with enough room for forgery.

2. Can't forge it as an IOU or IOU signature: there is written paper and the handwriting can't form an IOU, the signature on the document, the top label of blank paper, and the top label of blank paper.

3, to prevent the signature from being forged: you can write: signed by XXX, signed by XXX.