<P> On artificial surfaces, the field of play should be coloured green, ultramarine blue or signal blue . It is permitted for the run - off portion of the pitch to be an alternative colour . </P> <P> Goals consist of two upright posts placed equidistant from the centre of the backline, joined at the top by a horizontal crossbar . The inner edges of the posts must be 3.66 metres (4 yd) apart, and the lower edge of the crossbar must be 2.14 metres (7 ft) above the ground . The goalposts and crossbar must be white and rectangular in shape with width 50 millimetres (2 in) and a depth of 50 to 75 millimetres (2 to 3 in). </P> <P> The goal must be at least 1.20 m deep at ground level and at least 0.90 m deep at crossbar level . The goal area must be delimited at ground level by a goal backboard and two sideboards of height 460 millimetres (18 in). Affixed to these boards, the posts and crossbar is a net to stop the ball . </P> <P> The first hockey goals were "7 feet (2.1 m) tall posts placed 6 yards (5.5 m) apart" but were reduced to 4 yards (3.7 m) apart in the 1886 rules . In 1987, a rule was introduced so that at penalty corners "the first hit at goal should not cross the goal - line higher than 18 inches (460 mm)". This saw the introduction of a sideboard and backboard to the goals which are now mandatory . </P>

Is it sand or water on hockey fields