Files are essential when doing metal work.
They are worth far more than they are sold for.
You have immense amounts of control for fine tuning whatever it is you're building. ¹⁾

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Draw filing is a technique used to shape metal.
Hold the file perpendicular to the piece you're working on.
Use back and forth strokes only and it cuts material rather quickly.

Clamping the material to filed in vise:
The tang on the file can be held in either hand and the file can be used with either side facing the work piece.

This technique helps achieve, control and maintain square lines, a flat surface and edges better than a grinder.

Draw filing stainless steel with a bastard file 3)

It is essential to clean metal shavings from the file periodically with a wire brush.
Pull the file parallel to the teeth to remove the shavings, oil the teeth and continue.