How do I model a ribbon or banner with folds that pass behind each other?

The idea

A ribbon is not one shape. It is a front panel plus separate tail and fold pieces, each swept on its own and each cropped to its own outline. Modeling it as one sweep is what makes it look like a flat strip. The official banners and ribbons tutorial follows the order below. It shows the settings on screen only, so no heights or angles are given here. Judge them in the 3D View.

Steps

1. Organize the vectors. For every section of the ribbon you need two rails (its long edges), an open cross section, and a closed outline of the visible part of that section.
2. Two Rail Sweep each section. Select the two rails, click Use Selection, then pick the cross section and Apply. If the shape hangs the wrong way, click Swap Rail Order. If it twists, right-click a rail and choose Reverse Rail. Use Start New Component between sections so each stays separate.
3. Crop each section to its outline with Clear Component Outside Selected Vectors. Select the component first and the vector last.
4. Push the folds back. In Component Properties use Fade on a tail so it drops toward the point where it passes behind the front panel, or Tilt to lift the end that sits in front (see the entry on making one part sit in front of another).
5. Join the pieces for finishing. Use Create Component from Visible Model to get a single copy of what you see, then hide the separate pieces.
6. Sculpt the joins. Use Smooth and Smudge where sections meet so the folds read as one strip of cloth.
7. Mirror the finished half if the banner is symmetrical, nudge it into place, then run Smooth Components for an overall finish.

Pro tips

• The official tutorial uses the smooth filter for a broad finish and the sculpting tools for precise local work. Do the broad pass with Preserve Transparency checked so the ribbon edge stays crisp.
• Keep the separate swept pieces in the file, hidden. If the client changes the banner length you can re-sweep one section instead of starting again.
• Set ribbon components to Merge where they overlap other artwork, so the higher shape shows.