pole  and  shifting  his  body  weight  until  the  correct tension is read on the scale. This position can be held  steadily  and  comfortably  for  a  comparatively long  time. Measuring  distances  less  than  a  full  tape  length requires the use of the clamp handle (or “scissors clamp”),  which  is  attached  to  the  tape  at  some convenient  point  along  its  length.  The  handle permits a firm hold on the tape and furnishes a convenient  attachment  for  a  spring  balance.  When properly used, the handle will prevent kinking of the tape. READING THE TAPE.—  A chain tape may be either a PLUS (or ADD) tape or a MINUS (or SUBTRACT) tape. On a plus tape, the end foot, graduated in subdivisions, is an extra foot, lying outside the 0-ft mark on the tape and graduated AWAY  FROM  the  0-ft  mark.  On  a  minus  tape, the  end  foot,  graduated  in  subdivisions,  is  the  foot lying  between  the  0-ft  mark  and  1-ft  mark  and graduated  AWAY  FROM  the  0-ft  mark  and TOWARD  the  1-ft  mark.  As  will  be  seen,  this difference  is  significant  when  a  distance  of  less than a full tape length is being measured. Suppose that you are measuring the distance between point A and point B with a 100-ft tape, and the distance is less than 100 ft. Suppose that you are the head chainman. To start off, you and the rear chainman are both at point A. You walk away from point A with the zero-foot end of the tape. Because this is a plus tape, the tape has an extra foot beyond the zero-foot end, and this foot is  subdivided  in  hundredths  of  a  foot,  reading from  the  zero. You set the zero on point B, or plumb it over point B; then call out,  “Take  a  foot!”  When  the rear chainman hears this, he pulls back the first even-foot  graduation  between  A  and  B  to  point A, or plumbs it over point A. Let’s say this is the 34-ft  graduation,  The  rear  chainman  calls  out, “Thirty-four!” You  now  read  the  subdivided  end-foot  gradua- tion that is on or over point B. Let’s say it is the 0.82-ft   graduation.   You   call   out,   “Point   eight two!‘’ The rear chainman rechecks the even-foot graduation on point A and calls out, “Thirty-four point   eight   two!” As   you   can   see,   your subdivided-foot reading is added to his even-foot reading;  hence,  the  expression  “plus”  tape. Suppose now that you are measuring the same distance  between  the  same  points,  but  using  a “minus”    tape;  that  is,  a  tape  on  which  the subdivided  end-foot  lies  between  the  zero-foot  and 1-ft graduations. This time when you walk away with  the  zero-foot  end,  you  set  the  1-ft  graduation on  point  B  and  call  out,  “Take  a  foot!”  When he hears this, the rear chainman again hauls back the  first  even-foot  graduation  between  A  and  B to  point  A—but  this  time  this  will  be  the  35-ft graduation.   So   the   rear   chainman   sings   out, “Thirty-five!”  When  you  hear  this,  you  read  the subdivided-foot graduation on point B. This time this  will  be  0.18-ft  graduation,  so  you  call  out, “Minus   point   one   eight!”   The   rear   chainman mentally subtracts 0.18-ft from 35.00 ft and calls out,   “Thirty-four   point   eight   two!”   When   you are  also  acting  as  the  recorder,  recheck  the subtraction before you record the distance in the field   notebook. GIVING A LINE.—  The range pole is set on line  slightly  behind  the  point  toward  which  the taping will proceed. Line may be given (that is, the person with the range pole may be guided or signaled  onto  the  line)  by  “eyeball”  (that  is,  by eye-observation alignment by the rear chainman or someone else at the point from which chaining is  proceeding)  or  by  instrument. Slope Chaining The  methods  used  in  slope  chaining  are basically  the  same  as  in  chaining  on  level  ground. There are some differences, however, as follows: In slope chaining, the tape is held along the slope of  the  ground,  the  slope  distance  is  measured,  and the slope distance is converted, by computation, to  horizontal  distance.  The  slope  angle  is usually measured with an Abney hand level and clinometer; however, for precise measurement, it is measured with a transit. In  using  the  clinometer,  you  take  the  slope angle along a line parallel to the slope of the ground or along the tape that is held taut and parallel to the  slope  of  the  ground.  To  use  the  clinometer, you sight on an object that is usually a point on a  pole  approximately  equal  to  your  height  of instrument (HI); that is, the vertical distance from the ground to the center (horizontal axis) of the sight tube. While sighting the object, you rotate the level tube about the axis of vertical arc until the  cross  hairs  bisect  the  bubble  as  you  look through the eyepiece. Then, you read either the slope angle or percentage on the vertical arc and record it along with the slope distance measure- ment. The horizontal distance is computed, or in other  words,  the  tape  correction  is  applied. If  the  station  points  are  being  marked,  the corrections to the slope distances are applied as the  chaining  progresses.  These  correct  ions  are computed  either  mentally,  by  calculator,  or  by using a table. 12-13