A black dress with high slits for black tie adds movement and sensuality without sacrificing formality. The dress is usually floor length or midi with the slit creating visual interest as you walk. The slit might be in front or on the side. The rest of the dress is usually fitted or draped. The slit changes the proportion and makes the dress feel more modern than a plain floor length option. Fabric usually skims the body without clinging. The construction of the slit matters because the edges need to finish cleanly and the fabric needs to hold its shape. These black dresses with slits work for black tie because the slit feels purposeful and the rest of the dress stays elegant.