Making a continuation line on parts (e.g., Rod)

How can I make a continuation line on a part (e.g., a rod)?  Attributes gives me only
line types dash, dot, and so on.

What is the standard continuation line segment commonly used?

The default line type is continuous.

Heime wrote

How can I make a continuation line on a part (e.g., a rod)?  Attributes gives me only
line types dash, dot, and so on.

What is the standard continuation line segment commonly used?

Heime: What do you mean with continuation line? Simply a continuous line as dxli assumes or a line indicating an object continues further than drawn?

A line of an object that continues further than drawn.  

I'm still not sure what you are after.

If it's something like this there is no extra line type for it in LC. Maybe a straight dashed or ondulated or zigzag line.

Or do you mean a line going into endlessness, a ray?
Then you have to enable # construction line in the layer list. Then all straight lines will go into endlessness.

Quite right.  Like so.  Is there an undulated or zigzag line I can use?  Or would I have
to construct it from scratch?

I cannot use a straight dashed line because I have a number of adjacent elements.
And also use dashed lines as hidden elemental parts.

I want to indicate that the parts with the yellow lines an their end continue to the right
beyond the scale of the drawing.

As I said there is no special line type for this purpose in LibreCAD. You will have to construct it yourself. Once done you may reuse it by copying, shifting, rotating... You may even save it into the library.

A quick way to to draw an individual undulated line is by Spline through Points.