When levelling at a busy construction site, the instrument man gives the signal 'Movement of right arm by 30°'. What does this mean to the man holding the staff?
Correct Answer: A. Move top of staff to my right
📚 Detailed Explanation: Right Arm Moved 30° = Move Top of Staff to Operator's Right
Why A (Move top of staff to my right) is correct: When the instrument operator moves their right arm by approximately 30° (not a full horizontal extension), this is a plumbing signal — it tells the staff holder to tilt the top of the levelling staff to the operator's right, i.e., to bring the staff closer to vertical alignment in that direction.
Complete Hand Signal Reference
| Hand Signal | Meaning to Staff Holder |
|---|---|
| Right arm extended fully (horizontal) | Continue moving to the right |
| Left arm extended fully (horizontal) | Continue moving to the left |
| Rapid sweep with right hand | Move considerably to the right |
| Slow sweep with right hand | Move slowly to the right |
| Right arm moved by 30° | Move (plumb) the top of the staff to the operator's RIGHT |
| Left arm raised and moved to left | Plumb the rod towards the left (tilt top left) |
| Both arms raised | Stop; you are at the correct position |
Plumbing vs. Positioning Signals
| Type | Signal Form | Action |
|---|---|---|
| Position (move location) | Full arm extension, horizontal sweep | Staff holder walks left/right |
| Plumbing (tilt staff) | Partial arm movement (30° tilt) or raised arm | Staff holder tilts staff to vertical in that direction |
- Right arm moved 30° = plumb signal; “tilt top of staff to my right.”
- Full arm extension = position signal; “keep moving in that direction.”