Origami Envelope That Stays Closed. Or you could write a letter directly on a square piece of paper and fold the envelope from the letter itself. How to fold an envelope that stays closed without glue 1.
While not impossible to open without tearing, and requiring cuts as well as folds (which disqualifies the method as origami to an origami purist), there is a form of letterlocking that involves cutting a thin strip from the blank margin of the letter, folding the letter, and then punching holes through the letter with an awl, and threading the strip through the holes in an. Flip the paper and fold the right edge to about the center of the paper. Fold the flaps fold the right edge of the bottom section inwards, aligning with the crease you just made, and unfold.
