A snap collar (also called snap‑lock collar, starting collar, or ductboard snap collar) is a circular duct accessory used in HVAC systems. It is designed to be snapped together (i.e. the shell folds or latches) to form a rigid collar that fits into or onto a ductboard, plenum, or flat surface. Once snapped, it provides a connection point for round ductwork (in this case, 7‑inch diameter ducts). The “snap” mechanism allows for faster installation without welding or extensive mechanical fastening.

Snap collars are used to transition from flat surfaces (ductboard, sheet metal, plenums) to round duct, for supply or return branches, and they help maintain airflow integrity and structural support.