The Turkish-corner cushion, in my opinion, is not done enough. If you don't like the sharp corners you get with a knife-edge cushion, try Turkish corners. The treatment is called pinch pleating. This works on the knife-edge cushion and the box cushion when it is a scattered — not a seat — cushion. The pleats create neat, rounded tucks at each corner. This treatment is used to great effect on this blue-gray plaid back cushion.