There are other ways to increase the defense of a player, which is through prayers and potions that can be created through the herblore skill.
Potions, which help the Runescape defense skill, include the defense potion (+3-12%) and the super defense potion (+5-19%).
Prayers that can help defense include: thick skin (+5%), rock skin (+10%), steel skin (+15%), piety (+25%), chivalry (+20%), protect from magic prayer, protect from summoning, protect from missiles, and the protect from melee prayer.
These are just some of the many variations of how the skill of Defense in Runescape is used and helped.