A twin boundary of an organic single crystal can move easily under a small
stress. The boundary motion is intermittent, even under a constant stress.
The local velocity depends not only on external stress but also on the wait
ing time before the onset of motion. The present system is considered as a
simple system of dry Friction between two commensurate lattices. We found s
ome similarities between the twin boundary motion and solid/solid dry frict
ion.