noun
mountain fold
In origami, a fold that creates a raised ridge, like a mountain peak. The opposite of a valley fold (谷折り).
折り紙で鶴を作るときは、まず山折りと谷折りを覚えます。
When making a crane with origami, first learn mountain folds and valley folds.
Valley fold, the opposite crease direction where the paper is folded inward to form a trough.
Compound of 山 (mountain) and 折り (fold), referring to the mountain-like raised shape of the crease.