Thirds without a ruler (Haga’s theorem)

This device cannot show the 3D view. Follow the step pictures and text below instead.

1. 

   1. Find the middle

   White side up. Fold the left edge to the right edge and unfold to mark the middle of the top edge.

2. 

   2. Corner to the middle of the top edge

   Fold the bottom-right corner up to the mark in the middle of the top edge. Look where the folded bottom edge crosses the left edge.

3. 

   3. Mark and unfold

   Pinch a small mark at that point on the left edge, then unfold.

4. 

   4. Fold the bottom third up

   Fold the bottom part up along a horizontal line through your mark.

5. 

   5. Fold the top third down

   Fold the top edge down to meet the edge you just folded up. The paper is now in three equal layers.

6. 

   6. Unfold and check

   Unfold everything: the two creases divide the square into three equal strips. Use it to fold letters or split paper evenly!