[header] How to clean horizontal blinds [title] Keep the blinds slightly open. [step] Turn the stem until the blinds are mostly closed. The slats should be pointed at a downward angle toward you. 
It's important that the blinds remain partially open to allow you clean deep in between them. [substeps] You won't be able to fit the entire brush attachment into the blinds themselves, but the bristles will penetrate into their inner recesses and sweep the dust into the hose.