A wonderful idea! Knit up the bag, then place the placemat insize around the food to help keep it cold. At lunchtime, pullout the lunch mat, and place on your desk to have a clean mat to place food on. You will want to knit up many colors of bags and placemats for the entire week! Lunch placemat is just the right size, not too big. This makes a nice gift too! Uses worsted weight yarns, knitting needle US # 7, 16 inch circular.