A professional who aligns hairspring stud with center of roller and roller jewel with line of center on escape wheel pallet to ensure in-beat of watch movement. Responsibilities include:

• Positions balance wheel assembly in fixture of tool, using tweezers, and engages crescent of roller with lever to prevent balance wheel from turning.
• Engages slot in hairspring collet, using plunger, and turns collet and attached hairspring until stud on outer coil of hairspring is aligned with indicator on balance wheel.
• Observes minute parts, using loupe.