While looking for different foldout ideas for my notebook, I came across the Menko Envelope. It is too thick to fit easily in a notebook, but it is still practical origami.
The envelope securely holds small items or cards up to the size of the holding area. Starting with a square paper (as with most origami) the finished size is one-third of the original paper size. A six-inch page will result in a 2-inch envelope. What makes the Menko Envelope unique is that it has two layers of secure holding. Overlapping layers cover the holding area and flaps are folded over the layers.
Originally it may have been used for seeds and still works for that purpose. However, coins, SD cards and paper clips can easily fit as well. Anything that fits in the holding area and lays basically flat will work.
I recently used this envelope fold to send an SD card to a friend. I thought that the extra layers would provide protection during the shipping. I glued the envelope to a card, so my friend saw the Menko envelope upon opening the card.
Below is a sheet with instructions on how to fold. Following is a video demonstration which includes examples of uses. In both versions of examples, the instructions start with the paper already scored in thirds both ways – horizontal and vertical. There are methods to measure thirds by doing some pre-folds, but I find it easiest to take the dimensions of the paper and divide by three.
Using 6×6 paper, I made a mark two inches from the edge and folded the wider section to the mark, unfolded and then folded the narrower section to the crease (then unfolded). I rotated the paper 90 degrees and repeated this process to obtain the 3×3 grid.
In the illustration, gray lines are score lines and teal blue lines are fold lines. The red lines indicate folding directions.