My son and I have been discussing building positive credit, etc. He is 19 and would like to start building credit. He was telling me that a friend of his that is in a finance class at school stated that if you have a Mastercard debit card, when you make a purchase, you should always use the credit option instead of the debit option because it can build your credit. I have not heard of this, and I didn't really think it's true, so if anyone knows how true this may be, lemme know. I just thought that it can save you a fee, and needs the signature for purchase. thanks!