I have heard many MMs refer to "cross trades" or "crosses". What specifically does this mean? A trade between two MMs?
Cross Trading: Offsetting or noncompetitive match of the buy order of one customer against the sell order of another, a practice that is permissible only when executed in accordance with the Commodity Exchange Act, CFTC rules, and rules of the exchange. From my futures days (daze), a broker would be matching orders in his book without calling them out to the MM's in the pit.
If somebody can confirm, the orders that come to the floor at the open are probably what's left over after the buy and sells have been netted out.
A cross is when a broker lines up both sides of a trade instead of having a MM in the pit take the contra side. This can come about as a result of facilitation, where a bank has agreed to provide liquidity to a customer, or solicitation, where the broker will shop around for better pricing than the floor is willing to show.