Figuring things out

As all foreigners do, we are gradually figuring things out in our new environment, occasionally looking like i americani stupidi in the process.  Here are two stories on the subject, plus a little mystery you can help us solve.

Gary buys produce:  On our first shopping trip to the Coop, we bagged a half dozen kinds of veggies along with a boatload of packaged food and household items.  At the checkout, the clerk said something like "è necessario il peso di questo"--you need the weight for the produce.  So the produce bags were put aside, and Carmen checked out with the other stuff while I went off to customer service desk to score a pen to write down the weights.  The ladies at the desk were mystified by my plea "Ho bisogno una penna per ricordo the weight," lapsing into englitalian (itaglish?) when vocabularily challenged.  But they gave me a pen and I hustled back to the produce section with our bags.  I was vaguely aware that the clerk called the service desk, alerting them that a clueless americano needed serious help.  One of the service ladies caught up with me to show me how you put the bag on the scale, find the item on the scale display by scrolling through the pictures, select the item, and presto, the scale spits out a sticky tag with weight and price.  Too embarrassed to go back to the same clerk, I chose another line to check out.  To cover my wounded pride, I said little and all in Italian.  When checkout was complete, the clerk said to me: "Have a nice day!"

Carmen goes for cash:  Here, ATMs are called bancomats.  Having read internet stories that you needed an ATM card with a chip and/or a 4 digit PIN, I was gratified when my chipless card with a 5-digit pin worked at the bancomat in Incisa.  That was several days ago.  Today we decided to get more cash for the open-air market, and I considered us lucky to zip into a parking spot on the street about 50 meters from the same bancomat.  Carmen went off to make sure her card worked too.  She came back with a frown and said, "the machine said it is not possible with this card."  
    I theorized that the bancomat was out of money, a well-known phenomenon in Italy, but decided to test with my card.  I went down and had no problem.  Coming back, I said "I got cash with my card."
    "You went further down the street than I did.  I thought the bancomat was that machine under the sign with the big 'P'."
    I looked where she indicated and gently said, "Sweetheart, you just tried to withdraw 500 euros from a parking ticket dispenser!"

And now for something we haven't figured out.  Here is a picture of a typical Italian kitchen trash bag.  Notice the string attached to the very bottom of the bag.  We have been unable to puzzle out what the string is for.  If it is a string to tie off the top, why is it attached to the bottom?  We would enjoy hearing your comments on its purpose, whether firm knowledge or wild-ass guesses.

per quello che è la stringa?