Developing Drawing Strategies: Part 1 - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 103

The line ghosts, and because it is not a polyline yet, the command
line prompts you to turn it into one, as shown in Figure 4.5.
FiGuRE 4.5 The command line when a nonpolyline object is selected
5. Press the ↵ key to accept the default Yes option.
6. The command line now shows all of the possible polyline editing
options: Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/
Decurve/Ltype gen/Reverse/Undo]:.
To choose the Join option, enter J ↵ or click the Join option at the
Dynamic Input prompt that appears near the cursor (see Figure 4.6).
The intent here is to join the four lines into a single four-segment
closed polyline.
7. Select all the lines in the drawing, including the original line you
selected at the beginning of this exercise. Press the ↵ key when you
are done.
8. The second line in the command window shows 3 segments added to
polyline, indicating that the three subsequent lines selected have been
added to the original line that was converted to a polyline in step 5.
The bottom line indicates that you're still in the PEDIT command (see
Figure 4.7).