Rings are usually pinned in most Schneurle ported engines because the ports are so wide. In the older loop scavenged engines both the transfer and exhaust ports were segmented with 3 or 4 bridges to contain the rings. Simply by flicking one of these over for a few minutes you can watch the ring gap creeping around as the ring(s) rotated.

When assembling an auto engine it's just good practise to stagger the ring gaps to give the longest possible leakage path for the initial startup. After that, they'll rotate.