The mean trolls guarded the rickety bridge.

Meaning: This means that the trolls were guarding a bridge that was not very strong or stable. It's like saying, The trolls were guarding a bridge that was so weak, it looked like it could fall apart at any moment.

Choice of Words: Rickety is an adjective that describes something as weak or unsteady. Bridge is a structure that allows people to cross a river or other obstacle. When you add the adjective rickety to the sentence, it gives us a better picture of the bridge that the trolls are guarding.