I saw a video (I don't remember which one- or what it was about) but the person doing the video showed a way of, within the sketch merging two rectangles instantly within the sketch.  I cannot for the life of me remember how he did it.  I can't remember if it was an option or mode selected, or holding down a certain key (or both?). Anywhere the rectangles overlapped or were line to line, they would automatically merge into one continuous irregular shape.

Does anyone know what the trick to this is?  I can't even figure out what to search under: Boolean sketch? merge rectangles?

It was one of those things that I never knew about, though I've been using SolidWorks...well...for a very long time.

Anyone know what I'm talking about?