The A4 4-panel flyer
A four-panel flyer is a single sheet folded into four panels — usually an accordion that zigzags open, or a roll fold that tucks each panel inside the last.
Sheet sizesA4, A5, A6
Panels4
FoldAccordion or roll
FilesLayered PSD, smart objects
Opened right out it gives you one continuous landscape surface, wider than a tri-fold and without the inner panels reading as separate columns — good for a timeline, a product range, a set of steps, anything that wants to run left to right. Like a tri-fold it reveals itself in stages as it unfolds, so there's still a reading order to think about; the difference is that fully open it's one wide field rather than bounded panels, and that's usually the reason to pick it.
A4 is the full-size version for something detailed, while A5 and A6 fold down smaller for a lighter handout or a pocket piece. The fold style changes how it behaves — an accordion (or concertina) zigzags, so it stands on a table like a little screen and shows panels front and back as it opens, while a roll fold closes flatter into a slimmer folded size. Worth knowing which one your layout assumes before you set the panel widths.
In the sets: folded, part-open in the zigzag and laid flat, tented and shot from above, so you can present the closed cover and the full open strip together. Each is a layered PSD with smart objects — the artwork sits on its own layer, so replacing it leaves the fold, light and shadow untouched.