Near miss: We were traversing the A'Chir ridge (mod rock climb) on a somewhat wet and moderately windy day. There is a slabby section with tricky route finding and no easy bypass once on the ridge. We were fully kitted with a rope available and wearing helmets/harnesses. When the route became difficult with poor wet holds on steep slab, with a significant drop below, we did not take stock and get out the rope to secure our traverse. One member of the party became crag fast in an exposed position with inadequate/no footholds. This required the other participant to provide aid, in an insecure position, and a retreat backwards. We both agreed immediately that the rope was required and once a simple belay was set up the area was passed safely without significant difficulty or loss of time.