The A. Richard Putty Knife Putty Knife - Flexible (P-1 1/2-F) is equipped with flexible high-carbon carbon steel blades that are 0.05" to 0.065" thick. The full tang blades are heat-treated, tempered, ground, mirror-polished, and lacquer-sealed, which makes the blade hard and flexible, offering reliable, durable, quality workmanship. There is also a flexible taping knife blade that is hollow ground on both sides and a polypropylene, solvent-resistant handle. It's ideal to patch small holes and cracks.