heres a bit more info. Whats important to know is that during...

heres a bit more info. Whats important to know is that during that period although trading doesnt take place, any orders that are matched at the days closing price will still go through after pre-open finishes.

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from: http://www.camron.com.au/preopen.htm

Pre-Open Prior to Closing Phase:
Commences 04.00 pm. Concludes 04.09.59 pm.
Securities are not traded during the Pre-Open Prior to Closing Phase
Same process as the AM Pre-Open Phase.

Closing Price Auction:
Conducted at 04.10 pm.
Same algorithm auction price process as in AM phase above
All matching orders are transacted at the same Single Closing Price.


Pre open phase:
Securities are not traded during the Pre-Open phase
Limit Orders can be entered and withdrawn at any time during the pre-open phase.
Bid and Offer prices can overlap in the Market Depth.
The area of overlap is called "the match area"
Only bids and offers inside the match area participate in the opening auction.
The ASX algorithm calculates a weighted "auction" price (match-price) based on the quantities on each side.
As orders are entered and withdrawn, the re-calculated match price is displayed progressively.

also: http://www.asx.net.au/resources/education/basics/open_Close.htm

Google will have more info which might be worthwhile.