Perhaps you've seen one of these before.

Picture of card swipe reader with barriers above and below.

A couple of inches above and below the magnetic stripe reader are protrusions that allow just enough room to swipe a credit card. The barriers are a negative affordance (is that the right terminology?); they make swiping a credit card awkward.

I have to carefully place my card in the small space above the reader to start. After swiping I always end up jamming the card into the bottom barrier. If one wanted to apply Fitts's law to swiping a credit card, and intentionally violate it, this seems like a pretty good way to do so.

Yet, there must be a reason those barriers were added, and it doesn't appear to be structural.

Any ideas?

  • 1
    Regarding the terminology of negative affordance the answer is 'yes and no'. Broadly speaking affordance refers to the physical actions that can be carried out. In this sense, this design isn't negative affordance (you can still carry out the task) but the affordance has been inhibited (it is harder to do). However, affordance in HCI tends to mean "what the design communicates to you about how it can be used" (things that look like buttons can be used as buttons) and in this sense the barriers don't really change the affordance.
    – Splog
    Commented Jul 15, 2011 at 11:43
  • Maybe they want to make it harder to place fake card readers above them. Maybe some criminal will try to put another card reader above the existing one and they try to make this process harder by building barriers. Or maybe they want to create a feel of savety
    – BlueWizard
    Commented Jun 11, 2015 at 14:21

7 Answers 7


RedBox had a problem a few years ago with people installing credit card skimming equipment on their machines. The equipment was often attached to the existing credit card reader. It was big and bulky, but a lot of people wouldn't realize that it wasn't the right hardware. I thought these barriers were put in place to prevent the skimmers.

The Washington Post: RedBox Warns of Credit Card Skimmers

  • 4
    I'm pretty sure that link answers the question. The top photo shows the skimmer on the top and the bottom photo shows an "approved RedBox reader" with the barriers in question installed. Commented Aug 18, 2010 at 17:51
  • Looks like spammers/scammers don't limit themselves to ruining web-based interfaces (reminding me of captcha, password strength validation, etc)
    – cbosco
    Commented Aug 19, 2010 at 3:38
  • 2
    Crucially though it would have been straight forward to create a design that obstructs the installation of skimming equipment but does not obstruct the user from swiping their card.
    – Splog
    Commented Jul 15, 2011 at 11:39

The barriers protect against the installation of credit card skimmers.



When the credit card reader and blocks are positioned correctly you find that at least half of the credit card is inside the reader when you start swiping. This means that there is no way to place a skimmer on the machine that can capture the whole strip's data. Even if you had two read heads, one above and one below, there would still be a portion of the magnetic strip in the middle that cannot be scanned outside the existing card reader.


I am fairly certain I know the answer to this question. We are currently in the process of designing a kiosk and the big question is whether we will use an insert style MSR or a front swipe style MSR. With the insert style, which we have on over 100 kiosks, people jam things into them all the time and they need to be replaced frequently (they cost about $80 each). What we are finding with the swipe style is that people somehow miss the MSR and hit they card against the face of the kiosk both above and below the MSR. Even with a powder coated paint the kiosk will quickly become scratched and scarred. The reason is to reduce maintenance costs of replacing MSRs and repainting the kiosks.

  • Thanks! That's interesting, and sounds like a good reason to use front swipe instead of insert. But my question was about why the barriers are put above and below the MSR. The article linked in the accepted answer sounds like a plausible explanation. If you have a reason to be concerned about "skimmers," you should read that article and think about ways to prevent them. And maybe even ask this forum for suggestions on what might be a better way to solve the problem, given you have the advantage of still being in the design phase. Commented Aug 3, 2011 at 16:32
  • 2
    Also - try googling 'ATM Skimmer for Sale' to see what you are up against...
    – PhillipW
    Commented Aug 3, 2011 at 18:39

Perhaps it is to prevent the card from hitting the surface of the unit above/below the swipe? I have seen card swipes where all of the paint is worn away below the swipe from people rubbing the card against the surface. This is just a guess, it really doesn't seem all that useful.


My guess is that there's an issue with the reader itself:

  • It might not work when the card is swiped too fast
  • Or it might require the card to be completely parallel to the surface (i.e. the back)

If that's the case, then inserting the card with these barriers forces the user to do the whole thing (including the swipe itself) slower and increases the chances the card is insert perpendicularly until it hits the back.

Assuming they've discovered the card reader's limitations too late (or it was cheaper than the rest to begin with), the barriers are an easy fix.

Sounds reasonable?


Answering on if affects the usability, answer is yes. Which part of the usability and it is the perception of usage itself as it does not align with any other day-to-day usage patterns. It increases the cognitive load of the user in thinking how to avoid scratching the card while IN and OUT. Extraordinarily poor experience when it comes to motoring.

The hand movement is designed to perform an arc with ease improving the UX*. Alternative could be to design this as an arc and also balance the security/fraud concerns.

As usability expert of purist nature, we can never win over the other challenges and have to balance it with security/fraud and other necessary evils (from UX perspective) :)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.