Every now and then origami hands you a fold that feels completely different from everything before it. The open sink is that fold. Instead of creasing paper on the outside, you will take a whole section and press it back inside the model, tucking a triangle that used to stick out neatly into a recessed pocket. It is the move behind some of the most elegant finished models you will ever see.

Be patient with yourself: this one is genuinely tricky, and no one lands it perfectly on the first try. The ten steps below break it into tiny pieces — crease, flip, open the paper completely, then let the existing creases do the work as you close it back up. Take your time, and when it finally clicks, you will have unlocked a whole new tier of folding.

This is the most difficult fold in this guide. If you cannot fold it right now, do not worry — keep practicing and eventually you will get it. You will not see this fold in any beginner-level model anyway.

Step 1

For this example, start with a Square Base (the instructions for this base are later in this guide). Fold the top part of the model down along the dotted line. This is just practice, so do not worry about making your fold in exactly the same place as the diagram.

Step 2

Crease this fold very well, then unfold it.

Step 3

Turn the model over.

Step 4

Fold the top part of the model down along the dotted line. This will be along the crease you already made — now you are folding it in the opposite direction.

Step 5

Crease this fold very well, then unfold it.

Step 6

The easiest way to make the open sink in this example is to open the paper up completely.

Step 7

Push the paper inside the model, following the square of creases that you made.

Step 8

As you push the paper inside, start to close the model back up, folding along the creases that make the Square Base.

Step 9

Continue sinking the paper inside the model along the existing creases, and keep closing the model back into the Square Base.

Step 10

Your paper should look something like this. Fold everything completely flat.

The completed open sink. The dotted line shows the path of the paper inside the model: instead of sticking out as it did before, the triangle at the top is now sunk inside the model.