The purpose of rest seats in a removable partial denture is to provide:

Correct answer: B. Support (resist vertical/occlusal forces directed apically)

• A. Retention is provided by clasps (retentive arms that engage undercuts) — not rests.
• B. Correct. Rests and rest seats provide SUPPORT — they transmit occlusal forces to the abutment teeth and resist displacement of the RPD in an apical (tissue-ward) direction. Without rests, the denture base sinks into the soft tissue under occlusal load.
• C. Stabilization against horizontal forces is provided by reciprocal arms and major connectors — not rests primarily.
• D. Indirect retention is provided by indirect retainers (rests placed anterior to the fulcrum line) — a specialized form of rest, but the primary general purpose of all rests is support.