How to create spread guidelines

While within Designer View, you can create your own spread guidelines by double-clicking either the horizontal or vertical ruler:

You can also create these guidelines by going to the top menu and selecting View > New Guide

Select Horizontal to create a horizontal guideline or Vertical to create a Vertical guideline. Then, enter the placement value of where you would like this guideline to be placed on the spread (while using the rulers as a reference).  

Note: This feature supports negative placement values. For example, if a guideline is placed at the 2-inch (5.08 cm) mark, -2 (-5.08 cm) will place a horizontal guideline at the same distance from the bottom, so guidelines can be mirrored.