Hey, even a kind and generous teacher like me has to turn the occasional buck. Here's the official description from lynda.com:
In this week's free episode of Deke's Techniques, Deke McClelland shows you how to create the components for an entwined-rope pattern that you can assemble into a cohesive whole using Adobe Illustrator's Pattern Brush feature. Although Deke created a similar pattern around a circle a few episodes back (see "How to create a currency-style emblem"), today's approach results in a pattern that can successfully navigate 90-degree corners.
The entire pattern begins with a simple, unassuming line segment:
The wave pattern is created by applying the Zig Zag effect, setting the size to 4 points, and the number of Absolute ridges to 1.
Next, Deke creates the second strand of the twist by applying a Transform effect that reflects the now-wavy segment over the Y-axis:
He completes the pattern for the sides of the rectangle by copying one "link" of the twist and attaching it to the end. Deke duplicates those same two segments and rotates them to begin building the corner component of the pattern.
To make the looping design at the corner, Deke starts with a carefully measured Arc segment.
After rotating the arc into place, Deke lines it up and attaches it to the existing pattern. Translator's note: When Deke says "Mash-your-fist-J," he's referring the shortcut for the Join command that requires pressing Ctrl+Shift+Alt (or, on the Mac, Command-Shift-Option) along with J for Join. In the Join dialog box, you can tell Illustrator to create a smooth point at the join site.
Another duplicated version of the link shape, once Deke has truncated and rotated it, becomes the basis for the next part of the corner loop. Again, you join these endpoints to the existing path:
To create the very outer turn of the corner, Deke uses a modified ellipse. By measuring the distance he wants to cover ahead of time, Deke can tell Illustrator the precise dimensions he needs for the ellipse:
Once the ellipse is rotated, clipped in half, maneuvered into place, and joined up, the corner loop design is complete:
Deke uses a similar measure-draw-cut-and-rotate procedure to make the end segment. The results are three perfectly aligned components ready to serve inside your Pattern Brush. Below, I temporarily changed their stroke colors so you can see where each one begins and ends.