A painting knife is an artist's tool with a flexible steel blade used to apply and manipulate paint directly on the canvas.
Blades can be long and thin, triangular, rectangular or diamond shaped.
Their slender and limber blades usually have either a tapered or rounded tip.
Tangs are straight or angled to keep fingers from touching the paint.
[1] Famous knife painters are: Titian, John Constable, Bill Alexander, Bob Ross, Frans Hals, Rembrandt, Fragonard, Courbet, Nicolas de Staël, Marcelle Ferron, and Jean-Paul Riopelle.