"Shapes – insert ready-made shapes" says the tool-tip. I need to draw polylines, but even the F1 help says "no results found for polyline." What next?

[some minutes late] Ah, my mistake for using grown-up terminology … a web-search turned up the keyword "freeform". Unfortunately, I can't persuade either Freeform or Scribble to draw straight lines: I've tried holding down Shift before I draw, after I draw, while I'm drawing. All very frustrating! Hints and tips welcome.