The Query Boundary option allows you to automatically create a query exactly on a selected boundary. To use Query Boundary:
Select Query
Boundary 
from the toolbar or the Query
menu.
Use the mouse to select the desired boundary (i.e. excavation or ground surface boundary). Note that you may select only ONE boundary.
Press Enter or right-click and select Done Selection, and a query will be created exactly on the selected excavation boundary.
See the notes below about the Query Start Point, and the Query Locations.
Queries generated using Query Boundary are identical in most respects to queries created using Add Material Query, and are graphed, deleted, etc in exactly the same manner.
Right Click Shortcut
The Query Boundary option is also available as a right-click shortcut. If you right-click on a boundary, a popup menu will appear, from which you can select Query Boundary. This is a convenient shortcut for creating a query on a boundary.
Query Start Point
When you create a Query with the Query Boundary option, you will notice that a circular red dot is displayed on one vertex of the boundary.
The purpose of this marker is to allow you to identify which point on the Query corresponds to the first data point on a Query Graph. The red dot marker on a Query always corresponds to the first data point on a Query Graph.
Furthermore, for Excavation boundaries (which are always closed), it is important to note that the direction in which the Query values are generated, is always COUNTER-CLOCKWISE.
Therefore, when you are viewing a Query Graph for an Excavation boundary, the first point on the graph corresponds to the location of the red dot marker, and the values on the graph correspond to a COUNTER-CLOCKWISE direction along the boundary.
NOTE: the display of the red dot marker on queries can be turned on or off in the Display Options dialog, under the Queries tab, with the First point marker checkbox. In general you should leave this option turned on.
Query Locations
When you create a Query with the Query Boundary option, the query data is automatically generated along the boundary. It is NOT possible for the user to specify the number of intervals. This is because the boundary query generates the query data according to the boundary element discretization. This is controlled by the Number of Boundary Elements specified in Project Settings.
The boundary element discretization can be displayed on the boundaries by selecting the Show Element Discretization checkbox in Display Options. If you do this, and zoom in, you will see that the locations of the query data correspond to the boundary element discretization.
When you use Query Boundary, the boundary query data is calculated directly from the raw data computed for each boundary element (i.e. the values are "exact").