The Derrickhand or Derrickman position varies greatly from one drilling rig to another. He almost always reports directly to the driller. The name derrickman comes from the position that he normally occupies, which is at the top of the derrick. From this position he guides the stands of drillpipe (typically 90 ft long) into the fingers at the top of the derick while tripping out of the hole. When tripping into the hole he will pull the pipe out of the fingers and guide it into the top drive or the elevators. Traditionally the derrickman also works closely with the mud engineer (see drilling fluid) when not tripping pipe since he is not needed in the derrick. In this capacity it is his responsibility to monitor the mud weight (density), add sacks of chemicals (25-100 lb each) to the mud to maintain properties, and monitor the mud level in the mud pits to aid in the well control. He may also be responsible for the shale shakers on smaller rigs.