To Renovation ???? Return air grates are available in many sizes for approximately $5 at home centers. Test the measurements of obtainable grates and body the accesses a bit scaled-down. Place the assembly alongside the chalk line and fasten it to the bottom of the floor joists with 3-inch screws. https://medium.com/@a.l.e.xzhi.gl.at.y/luxury-living-below-elevate-your-toronto-home-with-a-basement-renovation-fit-for-royalty-18340e425584