Yes, you are correct. When roughing in receptacles with metal boxes, you typically install the plaster ring (also known as a mud ring or extension ring) at the same time as the box, before the drywall goes up.Here's why: Depth Adjustment

The plaster ring provides the necessary depth extension to bring the receptacle flush with the finished wall surface. Drywall thickness varies, and the ring accounts for this. You want the front edge of the ring to be flush with the planned finished surface of the wall so the device will sit correctly in the ring.

Support and Stability

The ring provides a solid surface for the receptacle to mount to, giving it added support and stability.

Ease of Installation

It's much easier to install the ring before the drywall is up. Trying to install it afterward is awkward and can damage the drywall.

Code Compliance

In many jurisdictions, having the correct extension ring installed before drywall is required to ensure the receptacle is properly recessed and safe.

In summary, install the metal box and the plaster ring together during the rough-in stage, prior to drywall installation. This ensures proper depth, support, and ease of installation for the receptacle. Flag for review