It is quite difficult to write on the front and the back of a piece of paper at the same time, using only the usual writing implements (pens or pencils).

Even turning the paper over so that the front is on the back and the back is on the front, doesn't seem to help much.

Making a möbius strip works, but a normal A4 sized piece of paper is too wide (or possibly too short) for this trick.

Therefore, what is needed is a specially designed apparatus.

This consists of a cast iron frame mounted on a mount,, The frame grips the edges of the sheet of paper using clamps arrayed a little like tenterhooks. The frame is mounted on a clamped ball mount so that it can easily be positioned in any convenient verticle orientation.

So far so good. Ambidesxtrous readers can jump straight to the annotate box and write their gushing praise. The rest of you can carry on reading.

A dual pantograph-cum-bell-crank type contraption has a soft fibretip pen at each extremity, actuated by a pencil shaped control rod. The user manipulates the control rod to raise and lower each pen from its respective side of the piece of paper, and to move it sideyways as the user "writes" using the control rod.

This device is obviously limited to writing _the_same_thing_ on each side of the paper simultaneously, but we consider this a huge technical advance on the previous situation
-- pocmloc, Sep 21 2021

(For ambidextrous writers) Mount paper vertically, so each hand can write on a side. Makes it hard to see what you're writing, but if you're good enough to write with both hands at the same time, you probably don't need to watch what you're doing.
-- neutrinos_shadow, Sep 21 2021


Did you know that most people, when writing on a chalk board with their dominant hand, can hold chalk in their other hand and make a reasonably decent mirror image of the what they are writing? (Line length is limited by arm length of course.) So I would be surprised if a non-ambidextrous person could learn to do that without much difficulty.
-- scad mientist, Sep 22 2021


Part of the point of the pantograph is to prevent the pen or pencil being pressed against the paper with too much pressure, potentially puncturing the paper.
-- pocmloc, Sep 22 2021


Just use a felt-tip pen or brush-tip or similar. Doesn't need (much) pressure.
-- neutrinos_shadow, Sep 22 2021



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