Another 20th Century invention with somewhat unclear origins, a curtains was an accessory to a hole in the wall called a Window. This enabled the user to view the outside world without risking the many unpleasant realities which going out would entail. The Curtains function in life was to Block this hole, thereby obscuring the outside world. This would prove useful when the user remembered why he made a house of brick to block everything out in the first place.

As a historical aside, the invention called the Window had a computer operating system named after it but unlike its namesake the Operating System was not clear.