WindowShade was a control panel extension 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 in addition to the double-click method of collapsing a window. The entire feature disappeared with the release of Mac OS X; windows could be minimized to the Dock or moved aside with Exposé on the new system. 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. WindowShade X from Unsanity stopped working in Mac OS 10.7, and other third-party developers have since released applications such as WindowMizer from RGB World that keep the WindowShade feature working on Mac OS X 10.6 and greater.
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.
Other operating systems 
Some 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. An intentional shading implementation for Windows is provided by third-party software vendors.