If the AllowSizing property is True for a column, the user can adjust the width of the column individually at run time. When the user points to the divider at the right edge of a column's header, the pointer changes to a horizontal double arrow, which the user can drag to resize the column in question.
Dragging the pointer to the left makes the column smaller; dragging it to the right makes the column larger. The column's Width property will be adjusted when the user completes the resize operation.
If the list does not display column headers (that is, the ColumnHeaders property is False), the horizontal double arrow will appear when the pointer is over the column divider within the list's data area.
If the user drags the pointer all the way to the left, the column retains its original Width property setting, but its Visible property is set to False. To make the column visible again, the user can point to the right side of the divider of the column that preceded it. The pointer turns into a vertical bar with a right arrow.
Dragging the pointer to the right establishes a new column width and sets the column's Visible property back to True.
You can prevent column resizing from occurring at run time by setting the Cancel argument to True in the ColResize event. You can always change the width of a column in code, even if AllowSizing is False for that column.