Support ring for concrete duct covering has inner and outer walls with upward projection on inner wall

摘要

The support ring for a concrete duct covering has an inner wall (3) and an outer wall (4). There is an upward projection (14) on the inner wall of the ring. The outer wall (15) of the projection can be angled inwardly towards the top. The inner face of the projection can be flush with the inner wall of the ring. The ring can be made of cement.