One of the simplest folds in origami, involving folding a flap of paper downward behind the rest of the sheet, forming what resembles a "mountain," or crest in the paper. In some origami books (mainly British books), mountian folds are also known as "peak folds." Most diagrams for how to fold origami show a mountain fold by a dotted and dashed line.

One of the simplest folds in origami, involving folding a flap of paper downward behind the rest of the sheet, forming what resembles a "mountain," or crest in the paper. In some origami books (mainly British books), mountian folds are also known as "peak folds." Most diagrams for how to fold origami show a mountain fold by a dotted and dashed line.