How to make a vertical line, as well as how to move it?

Answer 1

<hr style="position:fixed;left:5%;top:10%;height:100%;">

Answer 2

I wrote an example with full commented css, look at it: https://code.sololearn.com/WrkZ2BQnCvh3/#css

... and feel free to ask for specific explanations or helps to adapt to your case ( each context requires different solutions :P )