Step 1: Draw this shape in a dark
color to form a "flipped diamond"
shape.

Step 2: Draw a smaller triangle
inside of the "flipped diamond"
shape.

Step 3: Draw 3 sideways 'L's
between the shapes as shown in
the diagram

Step 4: Shade in different
sections between the lines drawn
in the last step as shown.

Result: Take a moment to look at
the illusion. Now try making it with
styrofoam, clay, or any other material
you have that can easily be sculpted.
Did you make it? You probably didn't.
The shading can be quite deceiving.
Get why it's called the "Impossible
Triangle"?