Pleat
A pleat is a pair of neighboring folds, one valley and one mountain, that creates a zigzag step in the paper.
Make a valley fold along the first line, then fold part of that flap back the other way along a second line parallel to it. Viewed from the side, the paper forms a Z shape, like one section of a folded fan. Pleats are used to shorten a flap, create stripes of alternating color, or, as in the Jumping Frog, build a springy section that stores energy.
Keep both folds exactly parallel; if they drift apart at one end, the pleat twists and the model sits crooked. Crease each fold separately and firmly before pressing the pleat flat. In the frog, a limp pleat is the most common reason the model fails to jump.
