I own a big old,old parallel drafting rule and a small one that is about
the size of a legal note pad.It has a hole in the middle of the cover
(sort of like the front of a hard back book) for the knob that lossens
and tightens the L shaped rule to fit through when the cover is
closed.The L shaped rule can be adjusted to any angle desired by
loosening and tightening the knob.It is a very handy little device for
drawing straight parallel lines on paper.I bought them at the Goodwill
store about ten years ago.I am not going to remove the cord (I didn't
know there is a cord in there) out of my big old parallel rule though.I
dont think my small parallel notebook size parallel rule drafting device
has any cord in it.They bough still work just as good as the day they
were made,perfect parallel lines.
cuhulin

The parallel rules used in drafting offices were about 5 feet long and
5 inches wide.They had long cords trailing out of each end that were
strung around pulleys mounted at each corner of the board (maybe
3'x5'). When properly set up the rules would maintain perfectly
parallel lines all over the board. Set squres were used on the top and
bottom edges to draw various lines. If you have a complete parallel
rule, it should have a lot of cord wrapped around it. Although the cord
is great for stringing dials, it would be a shame to wreck a perfectly
good parallel rule, although they are not used much these days. Those
old rules, primitive as they may be, helped design all the things from
bridges to radios from 1945 to 1980. Drafting machines were also used,
but they didn't have the ability to easily draw long parallel lines
such as those needed for structural steel, although they were good for
detailing parts.

I haven't looked at my big old parallel drafting rule since the day I
bought it years and years ago.Come to think about it,I think I do
remember it has some cords that are around the pulleys or whatever.It is
either in my old shed in my back yard (full of junk) or in my den. (full
of junk) Next time I stumble upon it,I will take a real good look at
it.I doubt if I will ever use it,I wont sell it or trade it off,if my
sister or brother wants anything I have,it's theirs for free.A few years
ago,I bought a magnafying glass that has a round flourescent light
around it and it is mounted onto a floor stand that looks like one of
those old,old floor lamp stands,I think it dates back to the 1940's or
sometime in the 1950's.She wanted it for her sewing room,I told
her,here,it's yours now.I like to buy old things simply because I like
to collect old things.All kinds of old
things,gadgets,radios,tools,whatever.
I have been a junk collector all my life,junk is in my blood.
cuhulin