Within a game's Preview Tab, you will find charts under the 'Line Move' section that illustrate how lines have moved over time. These are featured for the spread, total and each team's moneyline.
In the example above, the Heat opened at +4, which is shown on the left side of the chart. They moved to +4.5 and +5 in a relatively short amount of time before moving back to +4.5, which is where the line has remained for an extended period.