Trending Acrylic Nails Coffin Shape Black : There are lots of different nail shapes available but we chose coffin nails today because they are easy to wear, you can have long nails without the sharp points and it is one of the most popular shapes too. Coffin shaped nails are long with a flat tip and tapered edges, similar to a coffin. Acrylic Nails Coffin Shape Black / To shape acrylic nails at home, begin by trimming your nails to the length of your choice.