The model shows a one-sided ruled surface, generated by the movement of a straight line. There are given a circle k an a segment AB; AB is parallel to the axis of the circle and its centre M is situated on k (starting position). The plane through the axis of the circle rotates about this axis, and simultaneously AB rotates in this same plane about M such that the angle of the first rotation is twice the angle of the second rotation. In this way a ruled surface is generated, that is one-sided, because the segment AB, if M is in its original position, is rotated about 180°.

This one-sidedness in the model is illustrated by the red/white coloring of each segment, whereby the red pieces show the one part of the surface and the white pieces the other part and at some point the red part goes into the white part of the surface. Topologically this is a so-called Möbius strip.