ATF suggests that any padlock securing an explosives magazine have an American Society of Testing Materials ( ASTM) rating of at least 5 for “forcing” and “surreptitious entry.” ASTM’s publication, F883-97 “Standard Performance Specifications for Padlocks,” describes and grades various levels of performance for padlocks. Having the appropriate padlock will prevent easy access to thieves and help to thwart break-ins and robberies.</p