A mace is technically a strong, heavy wooden, metal-reinforced shaft, or just a metal shaft, with a head made of stone, copper, bronze, iron, or steel - generally with flanges on its sides to increase the force of blows. However, in the Redwall series, the term has become a synonym for a club with protrusions, for instance spikes or arrowheads, regardless of its construction material. Maces are used to deliver crushing blows which can injure an armored opponent, and the addition of flanges and spikes allows the mace to punch through armor to inflict grievous injury on an opponent. However, weighing more, they're slower to swing in a fight.
The mace was used extensively by Sunflash the Mace, which gave him his name. When first escaping from Swartt Sixclaw's band, Sunflash uprooted a tree trunk. Although it was at that time technically a club, after some time he added spearheads and arrowheads to make it a true mace. He carried it into battle even after he became the Badger Ruler of Salamandastron.