All you need to do is enter your library card number and your four digit pin code in order to borrow books. (goodereader.com)
We issue a card with 16 digit pin code which are sold at retail for cash and redeemed online. (onlinepersonalswatch.com)
You can also set up a four - digit PIN code of sorts that Alexa asks for when you buy something on the Echo, to prevent other people from spending your money. (howtogeek.com)