example
Say I create a solid that is 20 x 10 x 2 (let’s call this PART A)
I would like to create a piece of geometry that ‘mates’ to the 20 x 10 face, that is 20 x 10 x 100 (call this PART B).
I would like it to update as follows:
a) I adjust PART A to be 19 x 10 x 2. So PART B auto-updates to 19 x 10 x 100.
b) I reposition PART A, let’s say rotate it 90 degrees. So PART B also rotates 90 degrees (i.e. it is mated to the face of PART A so moves with this part).

thanks for the reply.
That’s frustrating, unusual and disappointing in equal measures.
We need to use Sketchup for this project, but this is the only tool I’ve used that doesn’t have this capability.

I guess components can kind of help when moving groups etc. but not having geometric constraints/mating seems nuts.

The two operations you described are both trivial using nested components. Can you elaborate about what you are trying to achieve so we can better understand what the best workflow is for you? It may be that writing custom dynamic components is what you need but so far it sounds like native tool will work just fine.

Thanks for the reply.
What you’ve described & demonstrated is all I’m trying to do.

The goal is have geometry that is ‘linked’, so when I resize/move parts then the corresponding part also resizes/moves. I’ll look into nested components. Thanks again.

“Nesting” is the term for placing components inside of other components. Here I have the two blocks you describe each a discrete component, I selected them both and made the pair into a new component. So now I have one component which contains the other two. Manipulations done to the outer component will affect everything inside as a unit together. If you need to manipulate one of the two separately just open the outer component for editing.

This could all also be done simply by selecting the two objects in question before performing an operation so that the tool acts on both objects, as was suggested earlier.

For me, the solution shown by endlessfix has little to do with “mates”. This is a common scaling without changing the geometry and requires associating these elements in a group or component, or selecting these elements simultaneously. It is not a change of one element and the other adjusts itself.
OP wrote “Can geometry be mated so adjusting ONE thing also adjusts the mated geometry”
As below