"Rounded Foot" would probably refer to a loose footed main. There is no bolt rope along the foot, and the sail is cut slightly rounded so the middle part will hang slightly below the boom. The only attachment points on the foot are at the tack and at the clew, where there is a strong sail slide, usually made of cast metal.I prefer loose footed mains as one has more control over the shape of the lower part of the sail, using the outhaul. They are easier to get on and off, and there is no baggy "shelf" along the boom.Peter.