Hi Dave Blocks protect environment from accidental corruption by blocking some operations. Here is the spec https://docs.google.com/a/canonical.com/document/d/1XFYlNGmQH7-X68IXhdxsANwHN6DgAL_RMn7IDK7ZbJc/edit#heading=h.ap4vrey3xxh6 Let me know if I could be of further assistance :D Sincerely Yours, Anastasia