Release 10.1A: OpenEdge Development:
ADM Reference

WindowFrameHandle

Handle of the optional Frame widget of a Window container.

Data type: HANDLE

Notes:

Read and Write.
This property only identifies the frame of a window container. This is not the same as ContainerHandle, which is the widget handle of the container in all object. In most cases the ContainerHandle is also the Frame handle for a SmartContainer.
Even if Window containers do not need a frame they often have one and in that case we must include it when, for example, resizing, widget-tree logic, and so on.