Even if you have given up paper lunch sacks for a reusable lunch box, you should still learn this trick. Why? Because it's about to make you the coolest parent or co-worker in existence. It's a great way to hold onto your lunch and it just takes a few quick origami folds. Over at Instructables there's always something new to learn. This time around it's a trick from a reverse engineered take out delivery bag. I still use paper bags in my own house for all sorts of things and this is a great trick to keep in the back of your brain for practicality and amusement.
Don't worry, you don't have to be an experienced origami master to take on this simple idea, it's only 3 folds and is easily adapted for both left and right handers. And don't think that this only works on lunch sacks; it will work on any paper bag, so give it a go next time you're carrying home groceries!