Gliffy provides guides to help you line up your shapes with other shapes. To turn on the Drawing Guides, click on the Drawing Guides button in the Toolbar. Now, when you drag a shape from somewhere on the stage or from the shape library, it will detect if another shape in it’s vicinity has a matching edge or center point. If there is a matching edge, the shape you are dragging will “snap” to the other shapes edge, and a green line will appear to show the alignment. The same goes with a center point, except the line will be red. See the image below as an example of a left edge and center point alignment on the X axis.