simply by putting groceries (-s...that's plural) in them. No, eggs don't need to go in their own bag. No, one pack of batteries don't need to go in their own bag. No, the one frozen item I bought doesn't need to go in it's own bag. Almost every time I get groceries bagged, they use about 8 bags when 2 or 3 would have done the job. And to the ninnies who complain about how things are bagged that make grocery stores bag groceries inefficiently, STOP IT. Luckily, I live within walking distance of the grocery store, so I usually just walk and take a folding cart with me. Just pile things in the cart and roll it home...no bags at all.