Local Knowledge is King! I used to work in a big old factory. I had been there for a long time, a part of the furniture! The funny thing is I was only a casual contractor but I had been around for years. They tried to replace me many times. Every time a new manager or boss was appointed I would be singled out as an unnecessary extra expense but they just did not have any one that knew the factory like I did. I knew every cable and what they were for. The older the factory got, the more they changed it, they never kept proper records either. The longer they kept doing all the wrong things more valuable my knowledge became.
They did not like me knowing more about there factory than they did. Sometimes I would have to act dumb but even that seemed to workout in my favour. I would be given more time to workout these complex projects but I all ready knew the best way to do them.
It was important to make the people that were giving me all the work look good. I would only ever give out information if directly asked, I liked to keep a low profile, no show boating. I would just focus on what I was getting paid to do.
Once I had to put together a scope on a project only to have it given back to me months later from a different manager who told me it was his idea LOL