Painting knives and palette knives are usually made from flexible tempered steel embedded into a solid wood handle and are a standard item in most painter's palette boxes.
Palette knives as their name implies, are used for mixing colors on the palette. They are usually 4" to 6" long and have a flat blade that extends out from the ferrule.
Painting knives come in a myriad of shapes and sizes, and provide a useful alternative to brushes for the application of paint to the support, particularly for impasto effects. They are distinguished from palette knives by the wire extension that attaches the blade to the handle, which bends down and then out again. This unique blade shape helps to keep one's knuckles from getting in the paint.
A painting knife blade is usually made of tempered steel, so that it is both stiff and flexible. It should not be too sharp, or else it may cut the fabric when scraping paint from a stretched canvas.