What's the difference between polyspast and truckle?

Polyspast

Definition:

• (n.) A machine consisting of many pulleys; specifically, an apparatus formerly used for reducing luxations.

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Truckle

Definition:

• (n.) A small wheel or caster.
• (v. i.) To yield or bend obsequiously to the will of another; to submit; to creep.
• (v. t.) To roll or move upon truckles, or casters; to trundle.

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