5:25 of "Modeling ducts"
In the demo, the instructor duplicates one face of the mesh, then re-adjusts the measurements of the duplicate face.
I am not seeing how to do that without pulling the other parts of the mesh around accidentally.
Is there a quick key I am not seeing, I am a little stumped.
eerikitect it should work without a problem; the long version is: select the Face, SHIFT+D, ENTER, then S (scale) or G(move) or R (rotate). You can also skip the Enter step and SHIFT=D and start moving your Mouse, or S or R.
Maybe you tried duplicating with ALT+D?
Or did you (accidentally hit O and) have Proportional Editing on?