A scanning mechanism (and a form of trading connectivity) that is used to find matches for incoming order flows/ indication of interest (IOI). This involves examining the trading blotters of participating brokers and dealers and generate messaging when a match is hit upon. This mechanism is often used by liquidity aggregation venues that deal with buy-side flows, rather than sell-side ones.

This form of trading connectivity is used by dark pools (block-oriented dark pools) to establish connection to client order management systems, whereby it helps portfolio managers, for example, to register the orders they entered in the system, circulating them until a cross is found.