Alignment guides are horizontal and vertical rulers that you can add to the Camera view and position anywhere in your scene to help you align elements to specific positions in the stage.
When an alignment guide is added, it is added to the scene. Alignment guides are visible no matter which layer is selected or which frame is the current frame.
Alignment guides are only visible when using the Transform tool. When manipulating an element with the Transform tool, it is possible to make it snap to alignment guides.