Gilts need to have good underlines to raise large litters of pigs, thus, teat accessibility, teat numbers, teat size, and teat placement is critical for proper function. Both rows of teats should point directly downward so they are completely accessible when the sow lies on her side. A good underline will have 6 to 7 teats on each side, with the teats spaced 2.5 to 3.0 inches apart. This allows for maximum mammary tissue development to feed the piglets and space for the piglets to nurse. The ideal teat size should be about the size of a pencil eraser so it will easily fit into the piglet's mouth. Some problems that can occur regarding teat structure include pin, blind, or inverted nipples. A pin nipple is a small (half the normal size or less) nipple between two normal teats that does not give milk. A blind nipple is one that looks like it has a BB at skin level in the end of the teat, giving it a flat look. An inverted nipple is one in which the BB is pushed up into the body cavity, leaving the look of a hole at the end of the nipple.