1. In Layout mode, click the Selection tool 
in the status toolbar.
1. In Layout mode, click the Selection tool in the status toolbar.
2. Do one of the following:
•Drag the part label or part boundary (the line that marks the bottom of the part) until the part is the height you want.
•To maintain the height of the entire layout while changing the size of one layout part, Alt-drag (Windows) or Option-drag (macOS) the part label or part boundary. (This causes the size of the layout part immediately below the part you're changing to also change.)
•To precisely resize a part, select the part by clicking its part label. In the Inspector, click the Position 
tab. Enter a value for the part's Height or Bottom boundary in the Position area. See Positioning objects on a layout.
You can also use the rulers, grid, and guides (choose View menu > Rulers, View menu > Grid > Show Grid, and View menu > Show Guides) to help with precisely sizing parts. See Using the rulers and grid and Using guides and dynamic guides.