Sol Lewitt is one of the pioneers of Conceptual Art, bringing his conceptual and geometric works to the masses after the Second World War. he’s pretty unsung in this country, though his influence is far greater than people realise.
He often worked with teams of people to help him create his massive wall drawings, often giving instructions as to how the works should be carried out, but vague enough to allow these volunteers to influence the outcome.
Sometimes they will include pencil marks filling in whole spaces with cross hatching, or grid patterns across a wall, but they all have a strong architectural quality to them (more so than his paintings) and these are some of my favourites that I could find…
A nice biography of Lewitt on Hollis Taggart website: http://www.hollistaggart.com/artists/biography/sol_lewitt/