Chapter 6  Building Layout
163
6.5.5 Running Straight
Lines with a Transit
Although the builder’s level can be used to
line up stakes, fence posts, poles, and roadways,
the transit is more accurate for these tasks, espe-
cially when different elevations are involved. Set
the instrument directly over the reference point.
Level the instrument and then release the lock
that holds the telescope in the level position.
Swing the instrument to the required direc-
tion or until a stake is aligned with the vertical
crosshair. Tighten the horizontal circle clamp so
the telescope can move only in a vertical plane.
Now, by pointing the telescope up or down, any
number of points can be located in a perfectly
straight line. See Figure 6-21.
6.5.6 Vertical Planes and
Lines
Beyond the leveling tasks just mentioned,
the transit is a good instrument for:
• Measuring vertical angles above or below
the line of sight.
• Plumbing building walls, columns, and
posts.
Measuring vertical angles
1. Position the instrument near the structure.
Level the instrument.
2. Release the lever that holds the telescope in a
horizontal position.
3. Swing the instrument vertically.
4. Set the horizontal crosshair at the point you
wish to measure.
5. Tighten the vertical clamp.
6. Make a final, fine adjustment with the tangent
screw to locate the horizontal crosshair exactly
on the point.
7. Read the vertical angle on the vertical arc scale
and the vernier.
Establishing plumb lines
Plumb lines can be checked or established
by first operating the instrument as shown in
Figure 6-22. As you tilt the telescope up and
down, all of the sighted points are located in the
same vertical plane. To plumb structures, such as
posts or walls, follow these steps and refer to
Figure 6-23:
1. Set up the transit at a distance from the object
equal to at least equal to the height of the
object. Tilt the telescope to sight on the base.
2. Loosen the horizontal clamp and line up the
vertical crosshair with the base of the object.
3. Tighten the horizontal clamp.
4. Tilt the telescope upward to the top of the
object. If the object is plumb, the crosshair will
be on the same plane as it is at the base.
5. If object is not plumb, adjust the brace to bring
the object into plumb.
6. Move the transit to a second position, prefer-
ably 90° either to the right or left, and repeat
the procedure.
A plumb bob and line may often be the most
practical way to check vertical planes and lines. For
layouts inside a structure, where a regular builder’s
level or transit is impractical, use a plumb line.
A B C
Figure 6-21. How to use the transit to align a row of
stakes.