Also known as integrated-mounting… The worktop is cut down at the point where the edge of the sink is set in, and the sink is glued down.  This process of instalment secures a flush surface between the worktop and the sink, which makes cleaning easier. (Integrated-mounting requires special tools). Note that prices and item numbers aren’t the same for sinks with normal insetting, sinks with under-mounting and sinks with flush-mounting.