A mallet is a piece of wood affixed to a short pole. The type of head can vary from a slightly rectangular prism (sometime with a slight parallelogram shape) mounted tranversely to a simple cylinder mounted tranversely or a cylinder (or near cylinder) with the handle mounted in the end. The last of these types is sometime termed a club is made of one piece of wood. They form a simialr function to a hammer.
They are often made of a knotty piece of wood as they are tough to split. When using tools that are designed to be struck use the general rule of like on like. Thus use a wooden budgeoning tool on a wooden handled chisel.