We can draw straight lines using a ruler. To position a ruler accurately, place the point that says 0 at the start of the line you are measuring. With the ruler placed carefully on the line ...

STEP 1: Using a pencil and ruler, draw a horizontal line. Set the compass to the width of the line. Place the compass at either end of the line and draw two arcs that cross in the middle.

And first of all, yes, the thing can indeed be used as a plain ol' ruler, or as a straight edge for drawing lines. It has laser-engraved numerical markings going up to 12 cm along one of its edges ...

and Highlighters assist users to make drawings on the slide. The Eraser removes ink from the slide. The Ruler feature draws lines and aligns objects against a straightedge. Click the Ruler button ...