Тhis strip has only one edge and one surface. The notions of left and right are meaningless here. It’s called Möbius strip.
To make one, you will need a long paper strip (ours has different designs for the front and the back). Twist the strip lenthwise at 180 degrees and glue the ends together.
If you cut it along the central line you will get an even longer, double-twisted strip.
If, however, you choose to cut it 1/3 from the edge, you will get two interconnected strips. One will be shorter, and the other will be a long double-twisted strip.
You can paint the magic strip without raising the brush from the surface.