Pencils
have
leads
of
different
____________________
in
a
scale
that
ranges
from
soft
(
B
)
to
hard
(
H
)
.
In
case
we
use
pencils
,
we
have
to
sharpen
the
lead
with
a
____________________
.
If
,
on
the
other
hand
,
we
use
____________________
pencils
(
also
called
propelling
pencils
)
,
we
don't
need
to
sharpen
them
because
they
use
replaceable
____________________
.
We
have
to
choose
both
the
hardness
(
usually
HB
)
and
the
thickness
(
usually
0
.
5mm
)
of
the
lead
.
Another
necessary
tool
is
the
____________________
.
It
is
made
of
rubber
and
is
used
to
erase
what
we
draw
with
a
pencil
or
mechanical
pencil
.
The
____________________
enables
us
to
measure
short
distances
in
centimetres
and
millimetres
.
The
____________________
____________________
work
together
to
make
parallel
and
____________________
lines
,
and
to
draw
some
angles
aswell
.
They
are
named
____________________
-
30
set
square
and
45
set
square
.
We
use
the
____________________
to
draw
arcs
or
circles
in
drawings
,
as
well
as
to
trasnport
segments
.
We
use
____________________
to
draw
angles
and
to
measure
angles
.
In
the
past
,
architects
and
engineers
drew
on
a
drawing
board
.
However
,
nowadays
it's
much
more
common
to
use
____________________
software
.
