Unless your system shows the match price, it is confusing.
What happens is that buyers and sellers watch the match price, not the bids and offers, which will be way out of sync. The highest bid may be 75, but the match may be say, 70. So if we want to be in the matching buy on the open all we have to do is bid at a price higher than the match price. If we are really desperate we would bid above the highest bid, which may or may not change the match price, depending on the size of the bid. Ie, we would bid above 75, safe in the knowledge that we will be getting our stock at 70.
If that sounds confusing, it is all revealed if you look at a screen that shows the match.
I remember clearly when there was no matching. The market opened at 10am and closed at 4pm, end of story. I have never been able to see any viable reason for the matching system.
SDL Price at posting:
55.5¢ Sentiment: Hold Disclosure: Held