Adobe Illustrator CS4 - Manual (Page 201)

194 USING ADOBE ILLUSTRATOR CS4
Painting
Draw texture on the left side of bounding box (left), and then copy texture and rectangle (right).
When the upper left corner point of the copy snaps to the upper right corner point of the bounding box, release the
mouse button, and then release the keys.
If you know the exact dimensions of the bounding box, you can select only the textures and use the Move command
to specify a horizontal move the width of the rectangle. Be sure to click Copy instead of OK in the Move dialog box.
6 Click outside the rectangle to deselect it.
7 Select the right rectangle, and delete it.
8 Continue drawing your texture with only the objects or lines that intersect the top side of the rectangle.
9 When you finish with the top side only, select all of the lines or objects crossing the top side and the bounding box;
then press Alt+Shift (Windows) or Option+Shift (Mac
OS) and drag downward to create a copy and to constrain
the move.
Draw texture on top side of bounding box (left), and then copy texture and rectangle (right).
10 When the upper left corner point of the copy snaps to the lower left corner point of the rectangle, release the mouse
button and then the keys.
11 Deselect everything.
12 Select the lower rectangle and any objects that don’t cross the top rectangle, and delete them.
13 Using the Pencil tool, fill the middle of the rectangle with your texture. Be careful not to intersect any of the
rectangle edges. Paint the texture.
14 Save the artwork and rectangle as a pattern swatch.
Defining artwork and rectangle as a pattern (left) compared to filling an area with the pattern (right)