How to move a component by a key point

How do I move using a key on component such as the center of a pipe and connect it to it’s corresponding pipe flange. The key points cannot be seen when they are brought together.

The easiest way is to toggle X-ray mode on.

View - Face Style - X-Ray

Or there is a toolbar button:

Very likely you can use Inferencing for that but you can also create those “key points” with either guidelines placed with the Tape Measure tool or some additional edges drawn in.

Also, for this kind of task it is sometimes easiest to move the component along one axis at a time using the arrow key constraints. Move it to line up on two axes while still separated on the third axis. Then pick any point on the face that wants to meet, move along the third axis until you see a snap for the face it must match.

Thanks Steve,

Yes that is an idea when drawing with the primitives.

I found an extension that does it more elegantly.

See the second video under,

Dave,

The tape measure inference should be able to pick the center of the faces
that I am trying to draw a construction line from? But does not seem to
happen with the components that is there from Pipedraft.

Apparently, It depends on the component that I am trying to connect with
the construction line. On one side, I have a flange that has a circular
end. Although the flange is also circular, it still symmetrical about the
longitudinal axis of the pipe. The other end that I have a grouped
component, an elbow, although the end is circular, it is not symmetrical
about the longitudinal axis and therefore does not inference and a center.
There must be ways one can tell SketchUp what one is trying to inference.
It has room for improvement.

Bingo. The Pipe Draft extension has that Inference built in. If I say
transform component and click the faces, It brings them to meet. This is
great.