Project body geometry
The same as projecting edges, but aimed at another part: click the edges of the underlying body or switch on “Face outline” above.

An external reference
When one part's sketch stands on another part's geometry, an explicit external reference appears between them. It is visible in the tree and it can be broken — unlike a silent dependency, which you learn about only when something has moved.
This is top-down design: the bracket's dimensions come from the housing instead of being retyped into it.
What to remember
Projected geometry is driven: it follows its source. Move the source part in the assembly and the outline follows — which is exactly what the link is for.