The sides of the box (before transformation) are parallel to the X-axis and Y-axis. The corners of the box can be rounded by means of quarter ellipses of the specified diameters. When the value of either diameter is 0, no rounding occurs. When the value of either diameter exceeds the length of the corresponding side, that length is used as the diameter instead. When the value of the diameters are equal to the value of the sides, the corners are rounded with a quarter circle. If the current position is (x0, y0), the box is drawn from the current position in a counterclockwise direction. This is significant when, for example, the area mode is BA_WINDING.

When correlating, the handling routine records a hit when the pick aperture intersects, or is completely within, the interior (even if the mix used for the fill operation is LEAVEALONE).