Billiard table ivory balls from warping. The first use of electric heating was for an 18.2 balkline tournament held in December 1927 between Welker Cochran and Jacob Schaefer, Jr. The New York Times announced it with fanfare: "For the first time in the history of world's championship balkline billiards a heated table will be used..." A pool table, or pocket billiards table, has six – one at each corner of the table () and one at the midpoint of each of the longer sides ( or ). Pool tables come in different sizes, typically referred to as , , , or tables.
Billiard table increase difficulty. The amount of (trimmed underside of the rubber cushion's protruding at the pocket opening), if any, has a strong effect on how easily a ball is accepted by the pocket (the ""). On snooker and English billiards tables, the pocket entries are rounded, while pool tables have sharp "". This affects how accurate shots need to be to get into a pocket, and how fast they can be when not dead-on, including shots that run along and against a cushion, making snooker more difficult to play than pool. According to the WPBSA official rule book, "the pocket openings