The Physical External Metals, Iron and Steel, give the two most well-known and visible forms of Allomancy - the ability to Pull or Push metals around you. The descriptions both mention "anchoring" by using a second large metal object to help you Push or Pull something too heavy for you to manipulate normally; both descriptions do so in their general rules areas, not within the stunt section, so clearly this action can be taken by any Mistborn, Coinshot, or Lurcher, not only specially trained ones.
However, their rules also state that you can only choose to Push or Pull either a single object, or else every object in range, and nothing in between without the use of the Multiple Targets stunt. The parts on Pushing and Pulling heavy objects don't specify anchoring as an exception to this rule, leading to an obvious question:
To perform an anchored Pull or Push without the Multiple Targets stunt, must you also Pull or Push every eligible metal object within your range? I'm leaning toward "yes, you do" but I'm not familiar with the book series (yet) nor do I have much experience playing or running Mistborn, so I'm not sure if there are canon examples or other rules I missed somewhere that would make it easier to use anchored Allomancy without needing to preemptively clear every scrap of metal from a 200 foot radius first.
(Just a note: there is a slight mismatch between the title question and the question in the text. Those really irritate me when I don't catch them, but in this case felt right to leave, so this is just a disclaimer so you notice it!)