Wavy edge to rectangle

Teresa,

You can:

1) Remove the fill, then click the corners at the end of the side in question with the Scissors Tool;

Now you have a line and an open rectangle;

2) Select everything and copy in front, then click the (top) line and press delete, then click the (top) open rectangle and Hide it in the expanded Layer in the Layers panel;

Now you have the original set to work with;

3) Click the line and apply ZigZag with an odd number of ridges per segment, then Object>Expand Appearance;

4) Select everything, then click the open rectangle once more, then in the Align panel apply the relevant left/right/top/bottom Align, then hold Ctrl/Cmd and press J;

Now you ought to have a rectangle with one wavy side;

5) Switch from Stroke to Fill;

6) Show the open rectangle from 2), then select everything and hold Ctrl/Cmd and press G;

Now you ought to have the desired appearence.

Edit: Missing crucial step included in 3), sorry.