Autodesk AUTOCAD 2006, Command Reference Manual, Page: 863 / 1490

If you enter y , the object is converted into a single-segment 2D polyline that
you can edit. You can use this operation to join lines and arcs into a polyline.
When the PEDITACCEPT system variable is set to 1, this prompt is suppressed,
and the selected object is automatically converted to a polyline.
Multiple
Enables selection for more than one object.
2D Polyline Selection
If you select a 2D polyline, the following prompt is displayed:
Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype gen/Undo]:
Enter an option or press ENTER to end the command
If the polyline you select is a closed polyline, Open replaces the Close option
in the prompt. You can edit a 2D polyline if its normal is parallel to and in
the same direction as the Z axis of the current UCS.
Close
Creates the closing segment of the polyline, connecting the last segment with
the first. The polyline is considered open unless you close it using the Close
option.
before Close after Close
Open
Removes the closing segment of the polyline. The polyline is considered closed
unless you open it using the Open option.
Join
Adds lines, arcs, or polylines to the end of an open polyline and removes the
curve fitting from a curve-fit polyline. For objects to join the polyline, their
endpoints must touch unless you use the Multiple option at the first PEDIT
prompt. In this case, you can join polylines that do not touch if the fuzz
distance is set to a value large enough to include the endpoints.
Select objects: Use an object selection method
If you previously selected multiple objects using the Multiple option, the
following prompt is displayed:
Enter fuzz distance or [Jointype]<0.0000>: Enter a distance or j
Jointype
Sets the method of joining selected polylines.
Paste Special Dialog Box | 839