The Available Widths toolbar allows you to select a panel or door width to be used in configuration.
You can select any width for building configurations.
This is strictly a visual representation that Panel Builder uses to allow configurations to be built.
When a configuration is saved, Panel Builder will automatically create all widths appropriate to
the configuration type.
Exceptions to this include when using Power Builder for Steelcase - Answer, and when setting a custom width or a field cut property.
See Use Power Configurations - Steelcase Answer.