How to make a long rectangular origami box

(page 7)

11th picture of long rectangular origami paper box

11.

Apply four "valley-folds" of the step #10.

Prepare to apply a vertical "valley-fold" .

12th picture of long rectangular origami paper box

12.

Apply the vertical "valley-fold" of the step #11.

Prepare to apply a vertical "valley-fold" .

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