A warder or jailer/gaoler; keeper of the keys in a prison.
To supply a turnkey product; to supply something fully assembled and ready to use
We can sell you all the parts, or we can turnkey the entire unit.
Ready to use without further assembly or test; supplied in a state that is ready to turn on and operate (typically refers to an assembly that is outsourced for manufacture)
They wanted a turnkey solution for the entire system, but we could only provide the enclosure.