When paying online, the general merchant will ask you to sign the purchase order, and the cashier will check the signature. No problem, the transaction is successful.

If you don't sign, many merchants will refuse to use your card. Most regular businesses have such regulations. If someone takes it away, the other party can sign the name directly, which is more likely to be fraudulently used.

You'd better use a ballpoint pen when signing. Pens and fountain pens don't dry easily, and they will be spent when touched. Ballpoint pens do not have this problem.