Riveting (again)

This action shot is trying to show how we get to this as described here.
Mr. M is using the rove iron to drive the rove onto the nail. His colleague outside the boat is holding the nail in place  with a holding iron, or bolster. When the rove is in place most of the protruding nail will be clipped off, the remainder being flattened out with a peen hammer so that it holds the rove in place permanently.
It is all well explained in the second link.