Just a note to 4get gto, Common sense dose not exist, there is no such thing, education comes by experience good and bad, as an apprentice trainer some learn faster than others and some you just can't teach usually because they have been corrupted or been put down by that very phrase, common sense can't be used as a defense in a court of law, people that use that phrase are often one eyed and ignorant of the value of education or are incapable of teaching and assume knowledge in others, it's a dangerous path to go down, that's how serious incidents happen, these are not accidents, not by a long shot.