Updated: Sep 26, 2020
This is much easier if you turn on the grid to begin with, so choose ‘view > grid > show grid’. It puts the appearance of graph paper right across the view. This won't print, it's just to help you position things. You can set up the number and units of divisions in preferences, but pretty much any grid will work for this.
Draw a line with the Line tool:
Select the node at one end with the Direct Selection tool. In the Properties panel you can tell it to become a ‘curved node’. Do this to the nodes at both ends. This automatically pulls the line into a curve at both ends. If the curve is too strong, just use the tool to pull on the ‘bezier’ handles and smooth it out a little.
When you’re happy, duplicate the line by holding ‘shift’ and ‘alt’ and dragging down. Then click and drag across both the ends on the left and choose ‘cmnd / cntrl + J’ to join them up. Then do the same thing with the nodes on the right. Then you have a rectangle with curved sides.
Fill it with a gradient. I’ve used a basic colour but added white at two places along its length, but you can colour it as you wish.
Then duplicate the entire shape. Again, hold ‘shift’ and ‘alt’ and drag down, so you have two shapes one above the other. Then, and before you’ve done anything else, choose ‘cmnd / cntrl + D’ (this repeats the last keystroke command’).
Then, using the ‘shift’ key to keep the shapes vertically aligned, pull them together so that you have a ribbon. I re-coloured two of them to create a strip of a different colour.
Group the object. Then, while it’s selected, double-click on the Rotate and Reflect tool.
Create a vertical copy set at 90 degrees, then move it down with the arrow keys until it looks like an extension of the ribbon. Again, recolour it as you wish.
And that’s how you create a ribbon. Well, one kind of ribbon. The next blog will create a different kind of ribbon.