The Solid Drill command performs Boolean operations onto flat 2D polygons by using overlapping 3D geometry. Modo uses the background layer geometry as the Boolean drill operator on the foreground geometry.
Core: Cuts away everything outside the 2D outline projected onto the polygons.
Stencil: Projects the 2D outline onto the polygons without removing either the inside or outside. Applies a default material to the new geometry within the outline.
Tunnel: Cuts a hole using the 2D outline and removes the inside.
Slice: Projects the 2D outline onto the polygons without removing either the inside or outside. This is the same as Stencil, but it does not affect the surface material.