Opening-only orders, posted stops, and paper fills as first-class rules

Order type inside the same procedure

The archive describes a listed-market workflow that placed opening-only buy and sell orders around a fair-value envelope, then moved into pairs trading and other sector work after the opening print. Only a subset of those opening orders was expected to fill. Unfilled opening-only orders canceled automatically after the opening print rather than remaining live.

Fills on those opening orders put the trader on the same side as the specialist under the listed-market rules then in force. Opening auction strategy, in that description, is a procedure that posts opening-only buys and sells around the envelope so that any fill shares the specialist side of the listed opening print and leftovers expire with the auction.

Opening-only leftovers and pairs work

After the opening, the described workflow shifted into pairs strategies and other sector trading. Pairs trading, as used here, is a post-open relative-value procedure that pairs related names or sectors after the opening book is resolved. Regional-exchange arbitrage was described as having dwindled because of limited public customer and broker order flow.

Editorial reading: an opening-only order that canceled after the print is a different rule from residual interest that stayed live into the pairs book. The leftover that expires with the auction is what keeps the specialist-side fill from becoming an unintended post-open order.

Posted stops versus mental stops

A sudden drop in the bid against an unchanged offer was presented as a setup for a negotiated lower print that could elect a resting sell stop before the quote recovered. That print is a trade-through: a print through the prevailing quote that can elect resting stops even if the quote later reverts.

Resting stop orders were characterized as revealing the exit to other participants. A posted stop is a resting stop that other participants can see or elect, including on a transitory negotiated print. Unposted mental thresholds let the trader reassess tape context first. A mental stop is an unposted exit threshold monitored against tape and book context rather than rested in the market.

Editorial reading: the posted stop is not a neutral translation of an exit forecast. It can be elected while the quote is still able to recover, which reverses the position before the forecast about price is shown to be wrong.

Paper fills at printed prices

Paper trading, as described, is a simulated-fill procedure that records hypothetical executions at printed prices without sending live orders. Those results were described as potentially misleading because assumed fills at printed prices ignore the effect of the trader's own orders on the quote, including at small size.

The recommended alternative to relying on paper results was to test new procedures with small live size, illustrated as 100-share orders.

Editorial reading: an assumed paper fill is another order-type rule. If the live order would have moved the quote, the recorded fill is not the same trade as the one the pairs or specialist-side setup would have received.

Reverse conversion

A reverse conversion was defined as selling puts, selling stock, and buying calls, with short-stock interest accruing to the stock-short side of the package. That package is the inverse of a conversion.