Alphabet Inc. (NASDAQ:GOOGL) shares are trading higher on Wednesday, but there’s an unfilled gap sitting just below the current price.

Traders are watching to see whether the stock pulls back to fill it — which is why we’ve made Alphabet our Stock of the Day.

If a stock closes at a price and then opens at a higher price, a ‘gap' or blank space appears on the chart. As you can see Alphabet gapped up from $350 to $375 at the end of April.

If a stock gaps or moves quickly through price levels and then eventually comes back to those same levels in the opposite direction, it can gap or move quickly back through them. This is what the old Wall Street adage ‘gaps tend to refill' refers to.

One of the main reasons support forms in a market is because of remorseful or regretful sellers. These are people who regret selling their shares when the price moves higher.

A number of these disappointed investors and traders decide to buy the shares back. But they will only do so if they can get them at the same price at which they were sold.

If a stock gaps up like Alphabet did, there is little or no trading at the levels that it gaps through. This means there are only a few or possibly even no investors and traders who sold at them.

Now that Alphabet has returned to the levels it gapped up through, it is making a rapid move back through them on the way down. The move is rapid because there are not a lot of buy orders between $350 and $375.

There are no remorseful sellers placing buy orders. The small quantity of buy orders means that sellers must undercut each other's prices to draw buyers into the market.

This can force the shares into a fast downtrend as it has with Alphabet. There's a good chance the shares continue to move lower as the gap is being refilled.

GOOGL Price Action: Alphabet shares were up 0.87% at $365.00 at the time of publication on Wednesday, according to Benzinga Pro data.

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