WindowShade was a control panel for the Mac OS that allowed a user to double-click a window's title bar to "roll up" the window like a windowshade. When the window was "rolled up", only the title bar of the window was visible; the part of the window that displayed the contents disappeared, allowing easier manipulation of the windows on the screen.
It debuted in System 7.5, but disappeared in Mac OS 8, when the feature was implemented as a part of the Appearance Manager. A widget was added to the title bar to reproduce the functionality. The entire feature disappeared with the release of Mac OS X; since windows could be minimized to the Dock or moved aside with Exposé, Apple decided there was no more use for it. However, several third-party utilities, such as WindowShade X for Unsanity's Application Enhancer software, have brought the concept of the WindowShade back to the Mac OS. It has since reappeared as a commercial haxie and offers other features, like translucent windows and minimize-in-place.
The WindowShade control panel itself stems from a third-party utility originally written for System 6.0.7 by Rob Johnston. Apple purchased the rights to this software from the developer for use in System 7.5.
Most window managers for Unix-like operating systems have a similar feature allowing windows to be set to "roll up" when the user double-clicks the title bar of a window. While Microsoft Windows does not expose such a feature by default, in some versions if a window is minimized while no taskbar is available, the said window will become a "shade" at the bottom of the screen. A "proper" shading implementation for Windows is provided by some third-party software vendors.