In a traditional origami diagram, a valley fold is indicated with dashed lines. To make a valley fold, simply fold part of the paper towards you and crease along the dashed line. Sometimes, you are asked to fold and unfold the paper after you make a valley fold. This is called precreasing. When you make a precrease, you are setting the stage for later steps in the diagram. Precreases are made at the beginning of the process; it is sometimes too difficult to put them into place accurately at a later time. In this photo, you can see several valley folds that are usually made to begin an origami box. In traditional origami diagrams, a mountain fold is indicated by a line made of dashes and dots. Sometimes, there will also be an arrow that indicates the folding direction. To make a mountain fold, fold part of the paper away from you and then crease along the line. You can do this by holding the paper in the air and folding it. However, it is easier to turn the paper over, fold a valley fold, and then turn the paper back to the original position. As with a valley fold, you may be asked to fold and unfold the paper to create a precrease that will be used later on in the process of completing a particular model. In the photo, notice how the creases that form a cross appear to rise up from the paper. These creases are the mountain folds. The squash fold is essentially a neat way of “squashing” your paper into position. It is a compound fold that is a combination of creases that are more or less performed simultaneously. As illustrated in the photo, you will be precreasing the model. Then, you will collapse it into the shape that is shown your instructions you are following. Two layers of paper open up from a central point. Look at your specific design instructions to get a feel for the correct placement of the paper during a squash fold. Some, but not all, squash folds are symmetrical. If you make a squash fold that is symmetrical when it is supposed to be off towards one side of the model will throw off all of the other steps in your project. Once you know how to make a squash fold, you can create a variety of origami models, ranging from flowers to animals. The origami organ base shown in the photo is made using a squash fold. Bases are important to know because they are the foundation for making more complex origami models.
