The Slide Master is a very important part of your presentation that influences the appearance of everything you see on the slide — from the slide background to the fonts used for text. All slides in your presentation may have different layouts — and each of these layouts may have different placeholder arrangements. However, they all share a common look — that look is provided by the Slide Master. Every presentation has at least one Slide Master. However, if you constantly keep adding slides from other presentations, you may have inadvertently added more Slide Masters to your presentation. So how do you know how many Slide Masters your presentation contains? And how do you add another one? In fact, why do you need another Slide Master at all?