If the selected object is a spline, line, or an arc, the following prompt is displayed:
Object selected is not a polyline.
Do you want it to turn into one? <Y>: Enter y or n, or press Enter
If you enter y, the object is converted into a single-segment 2D polyline that you can edit.
Before the selected spline is converted to a polyline, the following prompt is displayed:
Specify a precision <10>: Enter a new precision value or press Enter.
The PLINECONVERTMODE system variable determines whether the polylines are created with linear or arc segments. When the PEDITACCEPT system variable is set to 1, this prompt is suppressed, and the selected object is automatically converted to a polyline.