Many people have asked me to show how to cross hatch. It’s a skill you have to work at an be prepared t make lots of mistakes!
Basically it is using pen and ink to render tonal values. one layer of lines will give a an effect of grey, but when you cross hatch over the first set of lines with a second set, drawn at an angle to the first you make the effect of darkening the shade of grey in the area.
when you keep crossing at different angles the are becomes darker and darker until it is almost completely filled in.