One
is
the
major
blocks
of
the
drilling
line
is
a
____________________
,
the
construction
on
four
legs
standing
at
the
corners
of
the
substructure
and
reaching
to
the
crown
block
.
____________________
____________________
is
located
at
the
top
point
of
the
derrick
.
____________________
____________________
moves
up
or
down
in
the
derrick
.
The
heart
of
the
drilling
rig
is
located
on
a
____________________
____________________
.
The
drilling
line
is
put
into
operation
by
____________________
.
