In Expert mode, rulers, grids, and guides help you position items (such as selections, layers, and shapes) precisely across the width or length of an image. In Quick mode, only grids are available.
When visible, rulers appear along the top and left side of the active window. Markers in the ruler display the pointer’s position when you move it. Changing the ruler origin (the 0, 0 mark on the top and left rulers) lets you measure from a specific point on the image. The ruler origin also determines the grid’s point of origin.
Use the View menu to show or hide the rulers (Expert mode only), the grid, or the guide. The View menu also helps you to enable or disable the snapping of items to the grid or guide.