Although knee high boots, and open toe shoes are fashionable, and luxurious, your boss really doesn't want to see them, on you. They're pretty sexy and distracting, especially to your fellow male coworkers. If you want to be known as a sex symbol, that's is your business, but if you want to be taken seriously on all levels, cover up, even if it is just your feet. On a side note, heel height, in my opinion shouldn't matter (meaning between flat to about 5 inches should be the highest you go. If you go higher than that, then you are a brave soul, with a high tolerance for pain) and can make most women's feet and legs look better in those dress suits. Best wishes on your next job interview.