What is the black button on the fitting? A What is the black button on the fitting? This is an on / off switch. You can switch each adjustment individually as appropriate. Post navigationPrevious post: Are the lamps dimmable?Next post: Do you also have a physical address? Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment Name * Email * Website Save my name, email, and website in this browser for the next time I comment.