A round steel file (commonly known as a rat-tail file) is a versatile hand tool designed for smoothing, shaping, deburring, and enlarging circular openings, concave surfaces, and curved internal contours in metal, wood, or plastic. Crafted from high-carbon hardened steel, it features precision-cut single-cut or double-cut teeth along its tapered cylindrical blade. Essential components include a long, slim profile that tapers slightly toward the tip to access tight circular profiles, and an ergonomically molded yellow plastic handle that provides a secure, comfortable grip and precise tactile control during intricate metalworking, woodworking, and maintenance applications.