When you want to draw freehand waves and zigzags in Adobe Illustrator, the Pen tool produces an endless supply of Bezier curves and triangular sawtooth shapes. To build paths that lack hand-drawn irregularities and meet specific dimensional requirements, take advantage of some of Illustrator's tool- and technique-based shortcuts. You can turn a zigzag into a smooth waved sequence and build a pattern that extends as far as you want, creating regular, even results made up of sequences of identical shapes.
Press "P" to activate the Pen tool or click the tool's icon in the Adobe Illustrator Tools panel. Click your artboard to place an initial corner point. Hold down the "Shift" key, move your pointing device to the right and click again on your artboard to define the end point of a horizontal path.
Open the "Object" menu's "Path" submenu and choose "Add Anchor Points." Illustrator adds a new anchor point at the midpoint of the path. Repeat the Add Anchor Points step as many times as necessary to create points to define the waved or zigzagged changes of direction on the path.
Press "A" to switch to the Direct Selection tool or click the tool's icon in the Adobe Illustrator Tools panel. Shift-click on the leftmost anchor point -- the beginning of the path -- and every other anchor point from left to right. Because the Add Anchor Points command leaves all the points in a path selected, this action deselects each anchor point on which you click.
Click any of the selected anchor points, hold down the "Shift" key and drag either upward or downward to create a zigzag that extends either above or below the original vertical position of the path. Release your pointing device when the zigzags reach your desired size. To nudge the anchor points into position, hold down the "Shift" key and press the up or down arrow keys until the points reach your desired location.
Marquee around all the anchor points in your object, except for the first and last points that define the start and end of the path. Press "Shift-C" to switch to the Convert Anchor Point tool. In the Control panel, click the unlabeled Convert Selected Anchor Points to Smooth button. Adobe Illustrator converts all the selected points to smooth points and rounds each zigzag into a wavy shape. For a scalloped appearance instead of a sine wave, select and convert only the points you moved to create your zigzag.