Grunt supports various size modes for shapes (and indeed flags, charts, and other visual objects). Double click one of your shapes (or directly open the Shape rule). If you expand the section that says Size, you can change the width and height of your shapes. To the right of each option is a toggle button which allows you to toggle between the various size modes. You can choose between Automatic, Inherit, Relative, Absolute, Fit to content and Fit to size. With Automatic, Grunt will try to guess what might look nice. Inherit will try to look at other shapes behind your shape (if there are any) or default to Automatic. Relative allows you to set width and height as a percentage of the width or height of the container, while Absolute allows you to set width and height in pixels. Fit to content makes the shape as small as it can be (leaving space for content), while Fit to size expands the shape to fill its container.