For example , the name 18.2 balkline , one of the more prominent balkline games , indicates that balk lines are drawn 18 inches ( 457.2 mm ) distant from each rail , and only two counts are allowed in a backspace before a ball must leave .
So , for example , the name 18.2 balkline , tells us that balklines are drawn 18 inches ( 460 mm ) distant from each rail , and only two points are allowed in a balk space before a ball must leave that area .