The OA Sash is worn over the right shoulder. It is NOT an "automatic part" of your Field Uniform (Class A). Membership in the OA is shown by the pocket flap patch on your right hand pocket. The OA sash is only worn at OA events or when you are rendering service directly on behalf of the OA. A Scout never wears both their Merit Badge Sash and the OA Sash at the same time, nor should either of the sashes ever be worn hanging from the belt.
The flap signifies a Scout or Scouter as a member of a lodge. Members wear their sash at camp on Visitor's night for an OA call out ceremony. Members of the Unit Election Team wear their sash when they visit units to run an election. This is also an appropriate time for the members of the Troop to wear their sash.