Of course we can! Exclusivity means that there is only one person per seat in a chapter. A vertical is the specialty that a certain business can serve.
For instance, you can be a real estate agent, but there are real estate agents who specialize in serving people who want to buy investment properties, or people looking for commercial property, or people looking for residential properties. So it may look like a chapter can only fill one real estate category, but that category can be split vertically to allow for more chapter members who serve non-competing clients. (See article: Chapter Meeting)