Portrait and landscape
In most cases, you should lay out your app in portrait view. Users tend to hold their BlackBerry smartphone in one hand, and therefore, typically use it in portrait view. Plus, smartphones with a physical keyboard use portrait view exclusively.
Sometimes, landscape view can offer benefits and provide a better experience for all-touch BlackBerry smartphone users. Take movies and games, for example. Movies are made to be viewed in wide screen, and games often require two-handed interaction.
In some cases, you might lay out your application in both portrait and landscape view. This approach lets you provide a different focus in each view to enrich the user experience. For example, you could show a basic calculator in portrait view and a more advanced version in landscape view.
If you create custom UI components, make sure the components display correctly in both views. If you use BlackBerry UI components, they're designed to transition seamlessly if users switch between views.
Maintain consistency. Don't force your users to manually switch between views as they navigate your app. If a screen supports landscape view, any subsequent screen should also be available in landscape.
Don't create landscape views for smartphones with a 1:1 aspect ratio. Landscape mode is not supported on smartphones with a square aspect ratio.