Testing anvil rebound (a measure of hardness) is done by dropping a hammer (held lightly) or steel ball on the center of the face NOT swinging it or throwing it at the surface. A thrown object can bounce higher than the release point negates the validity of the test. Rebound is effected somewhat by mass and location on the anvil. Ring also indicates hardness somewhat but is more of a test of solidity of the anvil a clear ring indicating a tight face and lack of cracks. The shape of an anvil, the more narrow waisted, the louder and longer the ring.