The canvas is the main part of Dia. The Dia canvas is the window where all the user's objects will be placed on the screen and arranged. When the diagram is printed or saved, the contents of the canvas will be saved. Gridlines are similar to the lines on graph paper. They allow the user to easily align objects on the canvas. The gridlines can be hidden by going into File Preferences . In the Grid Lines tab, the user should click on the Visible button so it says No. Rulers appear on the top and the left of the Dia canvas. They show, in centimeters, how large your canvas is. On each ruler exists an arrow. The arrow moves on the ruler in coordination with where the mouse pointer is. For example, if the user moves the mouse up, the vertical ruler's arrow will move up, indicating the change. These arrows become useful when an object needs to line up exactly at a certain measurement point. Rulers, unlike gridlines, cannot be removed. The background color option allows you to change what the background looks like in the canvas. By default, the color is white. However, the color can be changed by going into View Diagram Properties Background and clicking on the bar. The bar displays what your background color is. The gridlines will change their color automatically to stay visible if the background color is changed to black. Zooming allows the user to get up closer to their diagram. This helps to let the user make precision drawings. The canvas can be zoomed up to 400%. Zoom can be done by clicking on the magnifying glass on the toolbox and clicking on the canvas. To zoom out, hold the shift button and click again on the canvas.