Various forms of faceted cuts, in which the gem is given a number of symmetrical plane surfaces, or facets, are universally employed in the cutting of diamonds and are used extensively for other stones as well. The most common cut is the brilliant. In this cut the top of the stone is ground to a flat so-called table from which the sides of the stone slope outward to the broadest portion of the stone, which is known as the girdle. Below the girdle, the sides slope inward at a slightly broader angle to a tiny flat surface, the culet, parallel to the table at the bottom of the stone. The ordinary brilliant-cut stone has 32 facets besides the table in the top portion of the stone (called the crown or bezel) above the girdle, and 24 facets besides the culet on the bottom portion of the stone (called the pavilion or base) below the girdle. In rare cases the number of facets is increased by some multiple of 8. Scientific studies have worked out proportions of the size and inclination of the facets that give the maximum brilliance to a given gem.