Constraints

The surfaces you specify on the Constraints tab of the Blast Block Polygons form, are used to clip the solids created using the dimensions you have set for Towards previous level and Bench height on the Wireframe and Direction tab.

As a rule of thumb, a blast polygon will be at crest level and the bench height is the extrusion of that polygon downwards. Note however, that constraints can be set so that polygons are extrapolated based on mid or toe contours, if needed.