Basic letterfold

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

1. 

   1. Crease the vertical centre line

   Place the rectangle tall, white side up. Fold the left edge to the right edge, then unfold.

2. 

   2. Fold both sides to the centre

   Fold each long edge to the vertical centre crease, making a strip with the two edges meeting in the middle.

3. 

   3. Fold the top flap down

   Fold the upper end down about one fifth of the original paper height from the top, taking all layers together.

4. 

   4. Fit the lower end under the flap

   Lift the top flap upright. Fold the lower end up so its tip fits inside the flap, then lower the same flap to close.