Essentially, the goal of opendoor is to grant access to special papers to any person that cannot afford it themselves. Usage: After opening a tab containing an article, press the extension on the top right navigation bar in google chrome. If the article you were looking for is listed, you're good to go! However, if the extension couldn't find the article on the page, you should find the DOI string (eg: http://doi.org/10.1093/ajae/aaq063), and paste it into the "Custom DOI" field.