The difference between files and rasps is clearly shown in Fig.

149.
It is a good rule that files and rasps are to be used on wood only as a last resort, when no cutting tool will serve.

Great care must be taken to file flat, not letting the tool rock.

It is better to file only on the forward stroke, for that is the way the teeth are made to cut, and a flatter surface is more likely to be obtained.
Both files and rasps can be cleaned with a _file-card_, Fig.148.

They are sometimes sharpened with a sandblast, but ordinarily when dull are discarded.
[Illustration: Fig.150.