By testing your product knowledge, your interviewer hopes to assess how capably you'd be able to serve their customers. So before your interview, familiarize yourself with Home Depot's product lines and offerings. Don't limit yourself to the power tools alone, but familiarize yourself with all of their products, from wheel barrels to nail guns to grinders to stereo speaker cords. However, considering that their offerings are extensive, assure your interviewer that if a customer ever asked you about a product that you weren't sure they carried, you would be resourceful in finding the answers your customer was looking for swiftly.