Carving chisels and gouges.
Lathe cutters.
Ratchet bit brace.
From the beginning tool-makers have shown skill in fitting a tool to the hand, as in the Eskimo skin-scraper; this simple adaptation may have arrived in copying the effect of wear. Other good hints have come from observing an implement after its work is done. At the places where mud clung to a plowshare the plow-maker was long ago told at what points to raise his metal; conversely, when a cutter of any kind is unduly worn at any part of its side, there the metal asks to be somewhat narrowed down.
Eskimo skin scraper.