A MainBar is a stack field that can be attached to the side (top, bottom, left, or right) of a frame’s form through its MainBar-related attributes (see
FrameExec Class and
FrameSource Class). These stack fields can be used to create toolbars.
For example, if there are two rows in each of the MainBar arrays, they are displayed like this:
For more information about creating toolbars, see the chapter “Creating Toolbars” in the Workbench User Guide.