During the Lightning Round segment of Mad Money Monday night one caller asked Jim Cramer about American Tower Corp. . In the daily bar chart of AMT, below, we can see that while the shares were weak in March and early April, the bigger picture is that prices have maintained an uptrend. The On-Balance-Volume (OBV) line made a low in March and a successful retest in May. Overall the OBV line tells us that there has been some more aggressive buying.