Ruler guides are nonprinting objects used for aligning content that can be positioned anywhere. There are two types of ruler guides: page guides and spread guides.
With nothing selected, click the Show Rulers button in the Properties panel to show the page rulers. Drag from either the horizontal or vertical ruler into the page or pasteboard area to create a guide. Edit guides by dragging them or selecting them to edit using the X or Y value in the Properties panel.
Use a guide for alignment by dragging objects close to the guide. When an object is close enough, the edge of the object will snap to (be pulled toward) the guide.
Drag the zero point on the rulers to start the zero on each ruler from somewhere besides the default upper-left corner of the page. Double-click the zero point to reset the zero on each ruler to the upper-left corner of the active page.
To lock guides, click the Lock Guides button in the Properties panel with nothing selected, or choose View > Grids & Guides > Lock Guides. To hide guides, click the Hide Guides button in the Properties panel with nothing selected, or choose View > Grids & Guides > Hide Guides.