Controller

One who, or that which, controls or restraines; one who has power or authority to regulate or control; one who governs.

An officer appointed to keep a counter register of accounts, or to examine, rectify, or verify accounts.

An iron block, usually bolted to a ship's deck, for controlling the running out of a chain cable. The links of the cable tend to drop into hollows in the block, and thus hold fast until disengaged.