Theme of this puzzle

• Fit as a fiddle and tough as nails
• Some tropes
• Poetic analogies
• Phrases with "as a" in the middle
• "Thick as a Brick" and "Solid as a Rock," e.g
• Animal analogies, often
• "Mad as a hatter" et al
• Like words?

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Simile \Sim"i*le\, n.; pl. Similes . [L., from similis. See Similar .] (Rhet.) A word or phrase by which anything is likened, in one or more of its aspects, to something else; a similitude; a poetical or imaginative comparison. A good swift simile, but ...

Wiktionary Word definitions in Wiktionary
n. (plural of simile English)