Why the tallest bar misleads
The London cash open is almost always busier than 14:30. A large histogram at 08:05 may be a normal open. A merely medium histogram at 14:40, if it is well above that half-hour’s recent average, can be the more serious market participation signal. Students who mark only rank order on the page miss this every week.
We do not require a statistical package. A pencil and last week’s print of the same clock windows is enough. In the chart pack we print a small table of typical half-hour volume for the three instruments we use, so the comparison is visible without leaving the paper.
Session shape before adjectives
Before you write ‘heavy’ or ‘light’, sketch the session in three blocks: open, midday, close. Note whether volume concentrated where the range was made. A session that spends its volume in the last hour defending a level is a different participation story from a session that spent it in the first twenty minutes and then went quiet.
This is also why we dislike a single cumulative line dumped on the chart without comment. The line can hide the clock. The clock is where the crowd actually lives.
A small drill
Take five consecutive days of one equity. Cover the prices. Mark only the volume histogram with the time axis visible. Circle the two half-hours that look unusual relative to their own history. Then uncover price and see whether those circles sit at useful places. If they do not, your eye is still chasing height.
Bring the drill to a reading circle if you join one. Week two is built around it, and unmarked pages slow everyone else.