Chapter 5 and Appendix C describes two sequences of experiments: the first involving reported presence measures and the second a screen-based spatial orientation measure. For the first sequence, a very small foreground occlusion was needed which could fit easily under an HMD. In the second, it was possible to mount a larger device on a tabletop in front of the monitor. Consequently, two completely different foreground occlusions were used for the two sequences of experiments, as discussed below. In both cases, the foreground occlusion was clearly perceived as being in front of the monitor.