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Figure 15-38.Using a Jacobs staff with a hand level.
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Equipment Operator Basic - Beginning construction equipment operators manual
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length. This stick is known as Jacob’s staff, as shown in figure 15-38. For rough work, you may ignore the use of a stick and merely use the height of your eye above  the  ground  in  your  normal  standing  position. The hand level is used for checking grade during the rough or early part of a construction project and is not used at distances greater than about 50 feet or even lesser distances if an accuracy of more than 2 or 3 tenths  is  required. DUMPY  LEVEL The  dumpy  level  (fig.  15-39)  has  its  telescope rigidly attached to the level bar, which supports an adjustable,  highly  sensitive  level  vial.  The  cross  hairs are brought into focus by rotation of the eyepiece and the  focusing  knob.  The  telescope  can  be  exactly trained  on  the  level  rod  by  lightly  tightening  the azimuth clamp and manipulating the azimuth tangent screw.  Depending  on  atmospheric  conditions,  the dumpy level can be used to measure vertical distances accurately at distances of 300 feet or less. When used for alignment, it is accurate at distances up to 1,000 feet. SELF-LEVELING LEVEL The  self-leveling  level  (fig.  15-40)  is  a  precise, time-saving  leveling  instrument  and  is  equipped  with a small bull’ s-eye level and three leveling screws. The leveling screws, which are on a triangular foot plate, are used to center the bubble of the bull’ s-eye level. The   line   of   sight   automatically   becomes horizontal  and bubble  remains remains  horizontal  as  long  as  the approximately  centered.  A  prismatic Figure 15-40.—Self-leveling level. 15-23







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