The signature strip on the back of the bank card should have the signature of the permanent card. The purpose is:

1 can prevent others from impersonating you to withdraw money or spend money at the counter. When withdrawing money or spending money at the counter, the waiter should check whether the signature is consistent with the signature on the card.

2. In case the card is swallowed when withdrawing money from ATM, you can recognize that it is indeed the user's bank card when you go to the bank to get the card.