The Ames Window is a variation of the Ames Room invented by Adelbert Ames.
The optical illusion of the bar passing through the window occurs because the window is not oscillating let-right-left as it appears to the viewer, but is in fact rotating with the bar. It is a trapezium (trapezoid) and the tallest end always appears to be the nearest to the viewer.
To see the effect, the viewer should stand about 12’ away, level with the window, and cover one eye.
The paper covering with its shaded frame gives the window a false perspective and is very important as the window must be flat for the illusion to work.
A strange extra illusion of these windows is if you hold it with both hands one each side, it can make one of your hands look bigger than the other.