RealGUIDE allows you single STL editing and boolean operations between two objects A and B:
Union: resulting STL being the union between A and B;
Subtraction: resulting STL being the subtraction of A from B;
Intersect with: resulting STL being intersections between A and B;
Remove intersection with: intersections between A and B are removed from resulting STL;
Cut with surface: the result is the same as above, but the resulting STL will have an open surface.
Warning:
Union, Subtraction and Intersect with will keep object A intact and object B will turn into the resulting STL;
Remove Intersection with and Cut with Surface will keep object B intact and object A will turn into the resulting STL.
If you want to keep both objects A and B intact, turn on option Copy the result as a new object. RealGUIDE will generate a new file as a result of the boolean operation.