The natural-media tools simulate the following real-world drawing tools:

- Pencil; gets darker the harder you press

- Pencil eraser; erases a wider area the harder you press

- Steel nib or quill pen: gets larger the harder you press

- Fine-point marker or Rapidograph-style pen; always one pixel, doesn't vary with pressure.

If you're using a pressure-sensitive input device (like a tablet), simply press harder to get the changes described, and use the heaviness slider in the Swatch Box to adjust the pressure response. 

If you are using a non-pressure sensitive device (like a mouse), you can use the heaviness slider to change the "pressure" for each drawing stroke.

As discussed in Layer Colors, you can change the color each tool uses, and you can erase with any of them. (The Eraser is the only tool that erases by default, but this can be changed as described in that section.)

You can only draw on bitmap layers with the natural-media tools. What you draw becomes part of the current bitmap layer as ink or graphite would go onto a piece of paper; to erase a mark you've made, you must use an erasing tool.

In the current version of Springboard, Edit > Undo undoes all drawing strokes made to the current layer since the tool was last changed.