I stick these on my tires for better traction on icy roads.

They are nothing, and do not exist.

This is not technically a hammer, but is struck by a hammer (sledge). It is used to reshape, while hot, the working end of a drill rod used in the ground and stone, etc.
Some have a pin in the center to line up on the airhole in drill rods that are used in rock and have an airhole running their length.