Furling refers to stowing a sail into a neat package after it has been handed, but leaving it still fastened in the position from which it can be set.
The headsail of a sloop (where roller furling is not fitted) is often lashed to a guardrail or along a bowsprit.
When bending a sail onto a yard, a square sail is usually furled at deck level, being tied to itself with gaskets, so as to provide a controllable package to haul aloft and fasten to the yard.
The stay or the luff spar to which the sail is fixed is rotated (usually by a control line on a drum fitted just below the tack, with the line lead back to the cockpit).
This general system was introduced in 1887 and there are various modern improved versions.