Sizing with the Mouse
By default, FlexGrid provides the resize and auto-size feature through column header cells. So, users can drag the right edge of the column header cells to resize columns, or double-click the right edge of the cell to auto-size the columns. This default behavior can be observed in the grid below.
You can use the allowResizing property to customize this behavior. Either prevent resizing altogether, or allow users to resize columns by dragging the right edge of ANY cell. This last option is especially useful in grids without column headers. For example: