When we want to describe someone as physically or mentally strong, we often use the phrase "tough as leather". However, there are other related synonyms that can be used to convey a similar meaning. Some examples of these synonyms include "sturdy," "resilient," "hardy," and "durable." Other words that can be used to describe this tough quality include "robust," "tough-minded," and "tenacious." These words can be used in a variety of situations, such as describing an athlete who has trained hard to become physically strong or an individual who has persevered through challenging life circumstances. Each of these words reflects a certain level of strength and toughness, and can be used to accurately describe individuals who embody these qualities.