Mastiffs aren't typically very good obedience dogs. They are just not that enthusiastic about the whole thing. I much prefer the Rally Obedience.

Above is one of my favourite pictures of Dexter (Banda 's Poin Dexter)
learning the 'leave it' command.
"If I close my eyes it doesn't really exist."
A picture of Maggie (BOSS Ch Banda N Cluny's Maggie Muggins, CGN, DD),
and Darwin (BISS Ch Banda N Cluny's Darwin), in a group down - stay.