The Guides Tool will allow you to position and display Guides over the image in the Viewer as an aid to getting the composition right and it is particularly useful when shooting tethered or cropping the image.
The Guides Tool is optimized to let you add the guidelines and adjust their location with a high degree of precision by entering a specific position value in either %, px, mm, cm or in.
The tool is available in Capture One Studio. If you are using Capture One Pro, please read about working with Guides here. All the Studio features are also available in Capture One Enterprise.