How to erase a very fine line on a drawing?

A couple of solutions.

One is to use an eraser shield. It is a thin sheet of metal with slots cut into it, one places the shield, with a cut lined up over the line, then erased with an ordinary erasure. The shield protects the paper around the targeted line.

Another solution is to use a softer eraser, such as an Art Gum brand. It is not as damaging to the paper even if one has to press harder to lift the pencil line.

Of course, the best solution is to learn to draw temporary lines with a much lighter pressure, making erasures much easier. The lightly applied line even makes lifting with a kneaded eraser possible.

Fine Line Drawings

I've used an Erasing Shield for that type of problem.

Through eraser simple

Have a retractable eraser handy. They come in different sizes. An example: http://www.amazon.com/Pentel-Retractable-Assorted-...