How the offset tool is supposed to work

I’m trying to use the ofset tool but no way !
I draw a line
I select the Ofset tool
I put my mouse on the line
I see a little red dot appearing
But impossible to get a clone of my line
Left Click & Drag
Right Click & Drag
Left,Right arrow
Up, Down arrow
Nothing works !

Is there any help somewhere ?

A single line cannot be offset. It can be copied.

Thank but I do no try first with a single line,

I first draw a rectangle then remove an edge of the rectangle
And now I want to offset the remaining edges to create the wall of an open “box”

Select all the edges.

And again from a different angle.

Thank you !
Got it !

My mistake was to forget to select the open Rectangle
Then I fall into the single line issue !