(thanks Mojo Savings!)
Each code is valid one time per credit/debit card. You will need to swipe your credit/debit card, but will not be charged unless you return it late (after 9pm the next night). In that case, you'd pay $1/day for each day it's late.
You can check the Blockbuster Express website for locations and to reserve online with a code if you'd like to!
*Also, check out the Redbox Master List of FREE Codes here, for codes that may get you free rentals as well! I haven't used any except "Breakroom" recently (which did work!), so be sure to let me know in the comments if they do or don't work for you, so I can keep it updated!