After working at a certain mass merchandiser for a few years, I can testify to the bag trick. I would say that it usually works 90% of the time. And why cashiers don’t type the card number in – the retailer I worked for required a supervisor to come approve it afterward, so most cashiers didn’t want to have to deal with that.
-DB
Hi and welcome to the SDMB! 
It helps if you include a link to the column so we can all get on the same page, so to speak.
I have personally had this work more than once.
Nutty.
When I was working in retail, a customer showed me this trick, when his own card wouldn’t read–only he used a strip of scotch tape. I continued to amaze people with the magical card-fixing scotch tape trick for years. I don’t recall it ever failing.
~mixie
God forbid the clerk should have to punch in the numbers by hand
It should be mentioned that punching in the number my hand takes a lot longer. Not only do you need the number but also (not on all machines, but on some for security reasons) the billing address, zip code, the ID number from the card, a manual swipe (with the old machines that went back and forth over some carbon paper) and to top it all of, merchant services will charge more for a card that is manually entered then one that is actually swiped.
You usually don’t need the bag, just push the front of the card against its side of the slot, which moves the card as far away from the magnetic read head as possible. It’s faster than futzing around with the bag to smooth out wrinkles.
Works with paper too.
For security reasons, cashiers are not allowed to type in numbers for credit cards. At least at my grocery store. Might end up typing in someone other then the person presenting it card number.
Plus, it effects our “score”. Stupid ELMS program. And the store has to pay more for processing maunally.
grumbles
I have seen this. I was told that by wrapping the card with paper and swiping several times, it would clean out some of the gunk that gets built up in the reader. I thought that you then had to remove the paper to actually have the card read.
You can’t punch numbers in for debit cards at all at any place I have worked at, although we could for credit cards. The bag trick worked well for me, I have seen it done by using tissue paper as well.
It also can be done with Food Stamp Cards. Since the majority of those cards are so worn out, 99% of the time I have to page a supervisor to hand punch them in. a real hassle. :mad:
plastic bags work very well for me and my cashiers.
btw, when we punch in the credit cards info as a last resort, we also imprint the card, to avoid employees ringing sales with stolen CC numbers…
I had the scotch tape thing work for me, so I left it on… my card wouldn’t read in ATMs and at the gas pump, so I had to take off the tape. Funny, that.