The top portion of a compression valve assembly, it holds the valve in place as it is tightened against the valve seat at the other end of the assembly
The shape of the bonnet varies greatly at different times; formerly the front part projected, and spread outward, like the mouth of a funnel
A metallic canopy, or projection, over an opening, as a fireplace, or a cowl or hood to increase the draught of a chimney, etc