Balkline is the overarching title of a group of carom billiards games generally played with two cue balls and a red object ball on a cloth-covered, 5 foot × 10 foot, pocketless billiard table. The object of the game is to score points, also called counts, by a player striking their cue ball so it makes contact with both the opponent's cue ball and the object ball on a single stroke. A player wins the game by reaching a predetermined number of points.[1][2] The table is divided by lines drawn on the surface, called balklines, into marked regions called balk spaces. Balk spaces define areas of the table surface in which a player may only score up to a threshold number of points while the opponent's cue ball and the object ball are within that region.[1][3]
The balkline games were developed to be more difficult to play and less tedious for spectators than the precursor game, straight rail. The top players of straight rail became so skillful that they would score a seemingly endless series of points, with the balls barely moving in a confined area of the table.[1][4] Straight rail, unlike the balkline games, had no balk space restrictions, although one was later added. According to Mike Shamos, curator of the U.S. Billiard Archive, "the skill of dedicated players [of straight rail] was so great that they could essentially score at will."[5] The development of balkline is characterized by a series of back and forth developments, where new rules would be implemented to make the game more difficult and to decrease high runs to keep spectators interested, countered by skill development to account for each new rule.[1][6]