So I cruised around the ATF web site and couldnt find an answer. I hope there are some people here who might point me in the right direction. At what point does a manufacturer of gun accessories need a federal manufacturer or gunsmith license? For instance, it seems a leatherworker who makes rifle slings doesnt, but I know that someone who takes guns to do engraving and refinishing does. Wheres the dividing line? Specifically, what about making sighting knick-knacks like scope rings? Links to law are more appreciated than opinion. Thanks.