If you are confident in your eye, use for cutting biscuitand a long knife (25 cm) with a serrated blade. First, cut the "hump" (the hill) with the surface of the cake. Measure the height of the cakeand in the middle, make a few slits to the inside, to designate half of the crust around the entire circumference. Gently push the crust with your hand and slowly rotating it counterclockwise with the other hand saw the knife toward you at the indicated marks. Cut deeper and deeper, continuing to rotate the cake. Move the knife further to the center with each new turn, until the cake is fully cut. So, a little sawing with precise movements, you will share the next cake in two.
Purchase a pastry divider, plastic, with string. Using it is very simply cut pieces of desired thickness. The device with the string for cutting biscuitand slightly reminiscent of a clothes hanger, the ends of which are rubber tips and multiple levels for strings. Device put rubber feet on table and slowly slide them through the cake, cutting it with a string strictly in the middle.
Some confectioners use twisted thread or fishing line. Wrap the thread around the cakeand on the required height, cross the ends and slowly pull them. The incision is fairly flat, but the biscuit may crumble much. In this case, the thread only mark the location for the cut and try to cut the cake at the target circle with a knife.