Trending Acrylic Nails Coffin Shape Black - Coffin shaped nails are long with a flat tip and tapered edges, similar to a coffin. A wide variety of acrylic nails shapes options are available to you, such as material, certification, and type. Acrylic Nails Coffin Shape Black / To shape acrylic nails at home, begin by trimming your nails to the length of your choice.