Matt Colie wrote:
It did not need to keep the ship from "slipping sideways" because the
rig of these vessels barely allowed sailing into the wind at all - by
modern standards.

Thanks for everyone's inputs. Basically, I was having a debate with a
friend (both of us don't know much about sailing). He was saying that
the old style sailing ships didn't have keels (in the modern sense,
where they obviously stick out from the hull), and I was claiming that
how can a sailboat work without a keel to keep the motion forward.