Daily Language Review follows the research-based model of frequent, focused practice to help students learn and retain skills. On day 5, a full-page activity provides a more extensive practice of a vocabulary strategy or skill, and gives students the opportunity to practice using the words in their own sentences.
All of the nouns used (hammer, chain, furnace, brain, anvil) are explaining mighty things that the tiger is being compared to. The poem is simply saying that they are smart, speedy, and strong.