In the theatre ‘blocking’ is the act of positioning your actors on stage, keeping in mind where they are and how they relate to one another.  When completing a piece of art, before adding in the finer details, I go through a stage of blocking as well.  Having established a solid foundation for the scene itself, I’m ready to add people.  Using rough shapes, and gesture lines I like to establish where my subjects will be positioned, how they will be positioned, and what they are doing.  I also use this stage to solidify heights and body types.  From this point I can move on to the finer, more intricate details.