turnkey

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.

Third World countries no longer want to purchase nuclear projects on a turn-key basis; they want to receive advanced technical training as well.

A system that is supplied ready to switch on and operate.

The hardware-software costs are packaged together. Turnkeys are either special purpose (e.g., only for one function such as libraries) or general purpose […]

A warder or jailer; a keeper of the keys in a prison.

He saw the same Turnkey unfetter a man / With but little expedition, / Which put him in mind of the long debate / On the Slave-trade abolition.

[…]they passed through an open door into a lobby, from which a heavy gate, opposite to that by which they had entered, and which was guarded by a stout turnkey with the key in his hand, led at once into the interior of the 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.