Long serving plates (長皿: naga-zara)serve a wide variety of purposes on a Japanese dining table.
Yakitori (Japanese chicken kebabs),whole grilled fish, etc. are just some examples of foods that may be too long to fit on a normal dish. Without having to cut up the food or have the food stick off the plate, the long serving plate is a multi-purpose tableware and an essential to Japanese dining.
They make great sharing plates as well. You can definitely find a few of these in the kitchen cabinets of many Japanese homes.