A double gatefold as shown in the figure below, requires a special folding machine attachment for automatic high-speed production. There is an easy way to do this without the attachment, but it does add a manual labor step to the process.
Step 1: Use your folder to make an 8pp accordion fold with panels ‘A’ on the outside. This fold uses 3 fold plates, usually #1, 2 & 3. Be sure to cut and fold ‘A’ at least 1/32” shorter than the center panels.
Step 2: Manually fold the accordion inside out with panels ‘A’ now facing each other on the inside of the fold.
An alternative: Do a double parallel fold (2 folds, first fold in half, then in half again) and then manually refold as a gatefold. While not as fast as the method above, it is probably a bit more accurate.
A third alternative works well for cover stocks: apply a high-quality crease to the sheet and simply fold the job by hand. This works best on stocks which are about 6 pt. or heavier.
Although you can successfully crease the beefier text stocks in order to eliminate cracking, you might have a hard time folding them entirely by hand. Be sure to experiment before committing to the whole job!
PDF report gives an overview of how to get better control over your creasing and scoring operations. Opens in new browser window.