The abstract nature of electric potential difference (voltage) can make it a difficult concept to grasp, but understanding the relative nature of voltage is central to developing a conceptual understanding of electric circuits. In laboratory situations, I see these conceptual difficulties manifest when students have difficulty placing voltmeter probes appropriately or struggle to interpret unexpected multimeter readings, such as negative voltages. I developed this lab activity to reinforce the relative nature of electric potential difference and to provide students with a concrete understanding of what a voltmeter measures, including the significance of the placement of each multimeter probe.