Part of Metal Type’s Printing Advice section, here Phil discusses creating accordion folds.
If this was just an ordinary job on light weight card stock of about 9 thou; I would just comp up a form of plain old type high scoring rules and go with that. Take the ink rollers out and run the stock through with enough impression so that the card stock folds easily.
I have often used hairline brass rule for this kind of job and scored all the scores or folds from one side.
But it all depends; for example, how thick the card stock is. If the card stock is 12 thou or thicker, then this scoring with brass rule from one side only, will not work. The results will be poor and there is a lot of danger that the stock will crack instead of folding like it should.
Steel Rule Dies
Also, it depends greatly how fussy one is. If you want a perfect result, then you are going to have to use proper steel scoring rule of less than type high and use a counter on the platen. Such material is readily available from the makers of steel rule dies. Tell them what you intend to do and on what press equipment and they will send the right material.
If the job or customer or the printer is super fussy, then you will need metal furniture between the scoring rules as this is the easiest way to obtain the exact measure between the scoring rules.
It is also very important how big the sheet of yard stock is. Or if the run is short, say only a couple of hundred and for some reason or other, a double run is required, well then don’t sweat it. Just run the job through twice.
So, I really do not know for sure what more to say. On the surface of it, this seems like a very simple job to me. But if you have never done this before, it may not seem so simple.