I can't claim any credit for the following method, I believe it originated in the Fleet Air Arm.
But if you can get your head round the instructions, it works a treat
WF.
Practice on a sheet of A4 first (stuff on one side, blank on the other),
this will help you avoid making a cock-up with the real thing.
Buy a nice shiny new chart from AFE so that you don't get your old and
new folds mixed up. Besides which, they were good enough to produce the
natty little badges, so we should make it worth their while!
Break the back of all the folds, i.e. make the fold one way and then
turn the sheet over and make it the other way, this helps the finished
chart to lie flatter.
Finish each fold by running along it with a lump of plastic, this makes
a fold a fold, not a bend.
Give yourself plenty of room on a nice big table and get a pal to help
you keep the folds from going wonky.
Be prepared to modify the instructions for charts that are taller than
they are wide, Scottish chart for example.
If you never want to look at the key panel across the bottom of the
chart, simply fold it back out of the way and treat the remaining area
as per the following instructions.
If you get it right you will end up with three horizontal and seven
vertical folds.
Right, if you're ready here we go.
Fold 1. with the chart printed side down, fold the two longest edges of
the chart together so that you get a nice fold running east west along
the middle.
Fold 2 & 3. Open out the chart and fold the lower edge up to the centre
fold, repeat for the top edge.
You should now have three horizontal folds running east west across the
chart. (If you haven't, give up and go down the pub!)
Fold 4, 5 & 6. Open out the chart and repeat the previous process, only
this time make the folds north south.
You should now have three horizontal and three vertical folds dividing
the chart up into sixteen little squares. (Fun isn't it) All of the
remaining folds will be north south.
Fold 7. Open out the chart printed side down and take the lefthand edge
and position it on the first fold in from the righthand side. Take a
soft pencil and write "not this one dummy" along the resulting fold
(You'll see why next).
Fold 8. Open out the chart again and repeat step seven again only this
time from the other end. By writing along the previous fold it will
hopefully stop you making fold 8 in the wrong place! Remember to fold
the edge to the FIRST fold at the other end.
You should now have five vertical and three horizontal folds, if not,
the pub option will apply.
Fold 9 & 10. Open out the chart and fold the lefthand edge in to the
first fold on the lefthand side. Repeat for the righthand edge to the
first fold on the righthand side.
You should now have completed all seven vertical and three horizontal
folds and all the vertical holds will be the same distance apart. No?
Pub!
Final assembly. Open the chart out flat on the table printed side down
and fold the top and bottom segments into the middle. Turn the chart
over with the open edges away from you. Starting with the top fold, make
the first fold away from you. Next fold towards you, next away and so on
until you have a series of concertina folds.
Open the folds out between the second and third peaks of the concertina,
turn it through 90 degrees and fold the top away from you.
The job is now finished (yipeee). To use, flip the chart open so that
there is an equal number of concertinas each side and page left and
right through the concertinas to see the centre portion of the chart. To
see the upper and lower portions of the chart, flip it over towards you
and page left and right through the concertinas.