<s>
Tools	O
such	O
as	O
pens	O
and	O
pencils	B-Device
mark	O
the	O
drawing	O
medium	O
.	O
</s>
<s>
A	O
drawing	O
board	O
was	O
used	O
to	O
hold	O
the	O
drawing	O
media	O
in	O
place	O
;	O
later	O
boards	O
included	O
drafting	B-Application
machines	I-Application
that	O
sped	O
the	O
layout	O
of	O
straight	O
lines	O
and	O
angles	O
.	O
</s>
<s>
The	O
tools	O
used	O
for	O
manual	O
technical	B-Application
drawing	I-Application
have	O
been	O
displaced	O
by	O
the	O
advent	O
of	O
computer-aided	O
drawing	O
,	O
drafting	O
and	O
design	O
(	O
CADD	B-Application
)	O
.	O
</s>
<s>
Although	O
a	O
variety	O
of	O
styli	O
were	O
developed	O
in	O
ancient	O
times	O
and	O
were	O
still	O
being	O
used	O
in	O
the	O
18th	O
century	O
,	O
quills	B-Application
were	O
generally	O
used	O
as	O
the	O
main	O
drawing	O
tool	O
.	O
</s>
<s>
Styli	O
were	O
also	O
used	O
in	O
the	O
form	O
of	O
ivory	O
or	O
ebony	O
pencils	B-Device
.	O
</s>
<s>
In	O
the	O
17th	O
century	O
,	O
a	O
stylus	O
that	O
could	O
draw	O
a	O
line	O
with	O
a	O
specific	O
width	O
called	O
a	O
ruling	B-Application
pen	I-Application
was	O
developed	O
.	O
</s>
<s>
The	O
basic	O
model	O
was	O
maintained	O
for	O
a	O
long	O
time	O
,	O
with	O
minor	O
modifications	O
,	O
until	O
the	O
1930s	O
when	O
the	O
German	O
technical	B-Application
drawing	I-Application
pens	O
came	O
to	O
the	O
market	O
.	O
</s>
<s>
Artists	O
(	O
including	O
Leonardo	B-Application
da	I-Application
Vinci	I-Application
and	O
Albrecht	O
Dürer	O
,	O
Nicholas	O
Bion	O
and	O
George	O
Adams	O
)	O
generally	O
made	O
drawing	O
tools	O
for	O
themselves	O
.	O
</s>
<s>
Industrial	O
production	O
of	O
technical	B-Application
drawing	I-Application
instruments	O
started	O
in	O
1853	O
,	O
when	O
Englishman	O
William	O
Stanley	O
(	O
1829	O
–	O
1909	O
)	O
founded	O
a	O
technical	O
manufacturing	O
company	O
in	O
London	O
.	O
</s>
<s>
Equipment	O
changed	O
radically	O
during	O
the	O
1990s	O
,	O
when	O
computer-aided	B-Application
design	I-Application
almost	O
completely	O
ousted	O
drawing	O
by	O
hand	O
.	O
</s>
<s>
Technical	O
design	O
has	O
changed	O
from	O
drawing	O
by	O
hand	O
to	O
producing	O
computer-aided	B-Application
design	I-Application
drawings	O
,	O
where	O
drawings	O
are	O
no	O
longer	O
"	O
drawn	O
"	O
,	O
but	O
are	O
built	O
from	O
a	O
virtually-produced	O
model	O
.	O
</s>
<s>
Traditional	O
and	O
typical	O
styli	O
used	O
for	O
technical	B-Application
drawing	I-Application
are	O
pencils	B-Device
and	O
technical	O
pens	O
.	O
</s>
<s>
Pencils	B-Device
in	O
use	O
are	O
usually	O
mechanical	O
pencils	B-Device
with	O
a	O
standard	O
lead	O
thickness	O
.	O
</s>
<s>
A	O
T-square	B-Application
is	O
a	O
straightedge	O
which	O
uses	O
the	O
edge	O
of	O
the	O
drawing	O
board	O
as	O
a	O
support	O
.	O
</s>
<s>
An	O
alternative	O
to	O
the	O
T-square	B-Application
is	O
the	O
parallel	O
bar	O
which	O
is	O
permanently	O
attached	O
to	O
the	O
drawing	O
board	O
.	O
</s>
<s>
The	O
drafting	B-Application
machine	I-Application
replaces	O
the	O
T-square	B-Application
and	O
triangles	O
.	O
</s>
<s>
A	O
drafting	B-Application
machine	I-Application
is	O
a	O
device	O
which	O
is	O
mounted	O
to	O
the	O
drawing	O
board	O
.	O
</s>
<s>
The	O
drawing	O
head	O
of	O
a	O
track-type	O
drafting	B-Application
machine	I-Application
slides	O
on	O
bearings	O
in	O
a	O
vertical	O
rail	O
,	O
which	O
in	O
turn	O
is	O
moved	O
along	O
a	O
horizontal	O
,	O
top-mounted	O
rail	O
.	O
</s>
<s>
A	O
drafting	B-Application
machine	I-Application
allows	O
easy	O
drawing	O
of	O
parallel	O
lines	O
over	O
the	O
paper	O
.	O
</s>
<s>
Rulers	O
used	O
in	O
technical	B-Application
drawing	I-Application
are	O
usually	O
made	O
of	O
polystyrene	O
.	O
</s>
<s>
A	O
ruler	O
with	O
a	O
straight	O
edge	O
can	O
be	O
used	O
with	O
lead	O
pencils	B-Device
and	O
felt	O
pens	O
,	O
whereas	O
when	O
a	O
technical	O
pen	O
is	O
used	O
the	O
edge	O
must	O
be	O
grooved	O
to	O
prevent	O
the	O
spread	O
of	O
the	O
ink	O
.	O
</s>
<s>
One	O
form	O
has	O
two	O
straight	O
legs	O
joined	O
by	O
a	O
hinge	O
;	O
one	O
leg	O
has	O
a	O
sharp	O
pivot	O
point	O
and	O
the	O
other	O
has	O
a	O
holder	O
for	O
a	O
technical	O
pen	O
or	O
pencil	B-Device
.	O
</s>
<s>
A	O
perspective	B-Architecture
machine	O
is	O
an	O
instrument	O
designed	O
to	O
create	O
perspective	B-Architecture
drawings	I-Architecture
.	O
</s>
<s>
It	O
is	O
primarily	O
suitable	O
for	O
pencils	B-Device
and	O
felt	O
tip	O
pens	O
.	O
</s>
<s>
Pencil	B-Device
marks	O
can	O
be	O
corrected	O
to	O
some	O
extent	O
with	O
an	O
eraser	O
.	O
</s>
<s>
Suitable	O
for	O
pencil	B-Device
and	O
felt	O
tipped	O
pens	O
,	O
and	O
with	O
limitations	O
for	O
technical	O
pens	O
.	O
</s>
<s>
An	O
eraser	O
can	O
be	O
used	O
for	O
pencil	B-Device
lines	O
.	O
</s>
<s>
Drafting	O
linen	O
was	O
formerly	O
used	O
for	O
technical	B-Application
drawings	I-Application
.	O
</s>
<s>
It	O
was	O
durable	O
and	O
held	O
up	O
to	O
handling	O
,	O
but	O
it	O
was	O
difficult	O
to	O
use	O
in	O
modern	O
whiteprints	B-Application
for	O
reproduction	O
,	O
and	O
shrinking	O
was	O
a	O
concern	O
.	O
</s>
<s>
Suitable	O
for	O
both	O
graphite	O
pencils	B-Device
and	O
technical	O
pens	O
.	O
</s>
<s>
Many	O
copies	O
of	O
technical	B-Application
drawings	I-Application
may	O
be	O
required	O
in	O
the	O
construction	O
of	O
a	O
project	O
.	O
</s>
<s>
The	O
blueprint	B-Application
process	O
was	O
first	O
used	O
for	O
mechanical	O
reproduction	O
of	O
drawings	O
.	O
</s>
<s>
Drawing	O
offices	O
may	O
use	O
diazo	B-Application
or	O
whiteprint	B-Application
processes	O
.	O
</s>
