Using the Rectangle and Rounded Rectangle Tool
The Rounded Rectangle tool draws rectangles with rounded corners, the Rectangle tool draws rectangles with square corners. To change the roundness of the corners, you use the Rectangle Roundness setting on the Property inspector. You can change the roundness of rectangles no matter which rectangle tool you use. As you did with the Ellipse tool, you hold down Shift to draw a square and you hold down Alt (Windows) or Option (Macintosh) to draw a rectangle (or square if you add Shift) from the center.