Hi Yeonghyeon

In order to get "square" like this:

you have to use such command sequence (draw polyline from left to right):

PL
PLINE
Specify start point:
Current line-width is 0.0000
Specify next point or [Arc/Halfwidth/Length/Undo/Width]:  <Ortho on> w
Specify starting width <0.0000>: 1
Specify ending width <1.0000>:
Specify next point or [Arc/Halfwidth/Length/Undo/Width]: 1   <-this is the end of 1-st "square" segment
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: w
Specify starting width <1.0000>: 0
Specify ending width <0.0000>:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:
Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: