If you cross fuse the left and middle images, you will see a gap with the left edge further. If you cross fuse the middle and right image, you will see the gap with opposite depth. There is no disparity in these stereograms.

• Sachtler, W.L.B., & Gillam, B. (2007). The stereoscopic sliver: a comparison of duration thresholds for fully stereoscopic and unmatched versions. Perception, 36, 135-144.