Right to left. After scoring a 1/2" line for the thumbnail shoulder with my marking gauge I rough shape the the curve with my large drawknife. Its weight helps to make it dexterous. Then I use my spokeshave to finish this part as seen in the middle picture. Now I carve the shoulder to complete the shape. The top rail of every arched panel everywhere for every application in the 18th century, whether on a Secretary of beautiful figured hardwood or on arched paneled pine walls and doors large or small, was done this way! >