The field of the stadium combines a number of elements for use in the jumping and throwing events. The long jump and triple jump areas comprise a straight, narrow 40-metre running track with a sandpit at one or both ends. Jumps are measured from a take off board—typically a small strip of wood with a plasticine marker attached—which ensures athletes jump from behind the measurement line. The pole vault area is also a 40-metre running track and has an indentation in the ground (the box) where vaulters plant their poles to propel themselves over a crossbar before falling onto cushioned landing mats. The high jump is a stripped-down version of this, with an open area of track or field that leads to a crossbar with a square area of landing mats behind it.