Where can you get a manual for a martin gas wall heater?

You can find a manual for a Martin gas wall heater on the manufacturer's official website, where they typically provide downloadable PDF versions of their product manuals. Additionally, you might check online retailers, home improvement stores, or forums dedicated to HVAC and heating appliances. If you have the model number, searching for it along with "manual" in a search engine can also yield useful results. Lastly, contacting customer service directly can provide you with the manual or direct you to where it can be found.