Balkline and straight rail

Balkline (sometimes spelled balk line or balk-line) is the overarching title of a large array of carom billiards games generally played with two cue balls and a third, red object ball, on a cloth-covered, 5 foot × 10 foot, pocketless table that is divided by balklines on the cloth into marked regions called balk spaces. Such balk spaces define areas of the table surface in which a player may only score up to a threshold number of points while the object balls are within that region.