Since the 1960s, LeWitt has made three-dimensional work using basic geometric units, such as cubes and squares, arranged in pre-determined mathematical sequences. He has written: ?To work with a plan that is pre-set is one way of avoiding subjectivity. It also obviates the necessity for designing each work in turn. The plan would design the work.? The objects are made by assistants according to LeWitt?s instructions. By minimising his physical presence in the process of fabrication, LeWitt emphasises the impersonality of these structures.