A valley fold is the most fundamental fold in origami. You fold the paper toward you so the crease forms a concave groove, like the bottom of a valley when viewed from above. If you’ve ever folded a piece of paper in half by bringing the top edge down to meet the bottom edge, you’ve already made a valley fold.
How a Valley Fold Works
To make a valley fold, you bring one part of the paper up and over toward you, so the two surfaces meet face to face. The crease left behind dips inward, forming a V-shape when you look at the paper from the side. This concave shape is what gives the fold its name. Every origami model, from a simple paper airplane to a thousand-step dragon, is built from sequences of valley folds and their counterpart, mountain folds.
The physical motion is straightforward: align the edges or corners specified in the diagram, hold them in place, then run your fingernail or a bone folder along the crease to flatten it sharply. Precision matters more than most beginners realize. A fold that’s off by even a millimeter can compound over many steps, gradually throwing off proportions until the model looks wrong or can’t be completed at all.
How to Recognize It in Diagrams
Origami diagrams use a standardized notation system developed by Akira Yoshizawa in 1954 and later expanded by Samuel Randlett and Robert Harbin. Published in Randlett’s 1963 book The Art of Origami, this system (now called the Yoshizawa-Randlett system) is used worldwide and makes it possible to follow origami instructions without reading any particular language.
In this system, a valley fold is shown as a dashed line ( – – – – – ) along where the crease will go, paired with an arrow showing the direction the paper moves. The arrow points toward you, indicating that the paper folds forward. Arrowhead styles vary between publications. Some use solid filled arrowheads, others use curvy or straight-edged ones, but the dashed line is consistent. After a fold is completed, diagrams show the resulting crease as a thin solid line.
Valley Fold vs. Mountain Fold
A valley fold and a mountain fold are mirror images of each other. Where a valley fold creates a concave crease (dipping down like a valley), a mountain fold creates a convex crease (peaking up like a mountain ridge). To make a mountain fold, you push the paper away from you instead of pulling it toward you.
Here’s the key insight: flip the paper over, and every valley fold becomes a mountain fold and vice versa. They’re the same physical crease viewed from opposite sides. In diagrams, mountain folds are drawn with a dash-dot-dot line pattern (..__..__..) rather than simple dashes, so you can always tell which one is being asked for. The Japanese terms reflect the same imagery: “tani” (谷) means valley, and “yama” (山) means mountain.
Most origami instructions favor valley folds when possible because folding toward yourself is easier to control than folding away. When a designer writes a diagram step as a mountain fold, it usually means flipping the paper first would create more confusion than just pushing the paper backward.
Common Mistakes to Avoid
The most frequent problem beginners encounter isn’t misunderstanding what a valley fold is. It’s making the fold inaccurately. Small misalignments early in a model cascade through every subsequent step. By the halfway point, the paper may not line up with the diagram at all, leaving you unable to continue or forced to backtrack and refold.
Paper thickness also causes issues, especially as layers build up. A phenomenon called “creep” occurs when the bulk of multiple layers shifts where the crease actually lands compared to where it should be. This is why some origami instructions specify making certain folds from a flat sheet rather than a folded one. For example, when folding the traditional crane, some diagrams fold the second diagonal from an already-folded sheet, which increases the chance of offset creases. Better instructions have you make that fold while the paper is still flat.
Another overlooked problem is hand placement. Most origami books don’t explain where to position your fingers or how to move them during a fold. A good general technique: hold the alignment point (where corners or edges meet) firmly with one hand, then sweep your other hand’s fingertip from that point outward along the crease line. This anchors the fold at its most important reference point before locking in the rest.
Practicing the Basics
If you’re just starting out, standard 15 cm (about 6-inch) origami paper is forgiving enough for learning valley folds. It’s thin, holds creases well, and is colored on one side so you can easily see which surface faces up after each fold. Models like the traditional cup, boat, or jumping frog use mostly valley folds and give you a chance to build accuracy before tackling anything complex.
Every fold you make should start with clear landmarks: corner to corner, edge to edge, or edge to a specific crease line. If a diagram asks you to fold to an arbitrary spot with no reference point, move slowly and check the next step’s illustration to confirm the result looks right before committing to a hard crease. A light preliminary fold lets you verify alignment before you press it flat.