How to constrain dimension to intersection with another plane?

[Anonymous]

I'm sorry if the title isn't clear. English is not my first language and I'm not sure how to summarize the problem in one sentence. Also, be aware that I'm a real Fusion 360 newbie...

Please see the attached image for more clarity.

I have a mid-plane with a sketch on it. I want the rectangle to be as deep/wide as to were it intersects with the side panel (yellow dot). I tried adding a construction line on the side panel, but I'm unable to select it when trying to set the dimension constraint on the sketch.

Any advise on how to achieve what I would like to do?

[jeff_strater · Accepted solution]

I think what you want to use is the "Intersect" command:

and select the "bodies" as the selection filter:

This will create a set of curves, in the active sketch, which represent the intersection of the selected body and the active sketch plane.  You can constrain to those curves