Counterweight and barrel: what they have in common

1. Step 1. Counterweight — is used in — Drawbridge. A counterweight.
2. Step 2. Drawbridge — is a kind of — Bridge. A bridge.
3. Step 3. Bridge — has part — Arch. Stone bridges were built as arches.
4. Step 4. Arch — works like — Barrel. Staves squeezed by hoops hold their shape by the same compression as the stones of an arch.

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