WindowFrame

WindowFrame is an option for notebooks that determines the type of frame to draw around the notebook window.

Possible settings are as follows.

The details of how particular types of frames are rendered may differ from one computer system to another.

Settings for WindowFrame affect only the appearance of a window and not any of its other characteristics.

See The Mathematica Book: Section 2.11.13.

See also: WindowTitle, WindowElements, WindowToolbars.