The first way is roller reefing. This was used on Macgregors until he started making the 26. With roller reefing the sail is wrapped around the boom. With this setup the sail can be wrapped as many times as the captain wants to reduce the sail area to the desired area.
The second way is slab reefing. The sail must have reef points installed in it in order to reef. The reef that Macgregor installs in his sail is where most sailmakers install the second reef (50% reduction). It is nice to have the first reef point (25%reduction) because there are many times that all that is called for is a 25% reduction.
In my sail I have installed the first reef point.After using these two reef points for several years I think I have finally set them up correctly. I will try to explain how I set them up.At the clew I have set up permanent lines through the two reef points. Each of these lines attach to the boom on one side and the line goes up through the cringle and down the other side to a cheek block and then forward a couple of feet to a captive clam cleat. At the tack I have a line permanently tied to the tack ring in the sail. From there it goes up the starboard side of the sail and then between the mast and sail, through the first reef cringle and then down through an eye on the boom and to a cleat on the mast. There is a slug about half way to the first reef. There is a sail stop about 10 inches up from the boom. When this first reef is tied in the slug is not removed from the groove. This slug holds the sail by the mast up above the boom and forward. After the clew is tightened up the sail will stay above the boom and ties through the other grommets in the sail are unnecessary. If I want a second reef I first put in the first one and then put in the second one. The first reef line (that is cleated on the mast) on the mast is fed up the starboard side and between the mast and sail just under the second reef point. Then through the cringle and down to the cleat again. There are then two slugs sitting on the slug stop and again the luff of the sail is held up and forward. Again the sail will not drop below the boom. At the clew the second line is tightened and fastened in its clam cleat.
The dimensions on my sail are
Tack to slug stop 12
The purpose of running the reefing lines this way is to provide reef that is neat, looks organized and doesn'r require the removal of the lower slugs from the track. It also makes it unnecessary to tie lines through the small gromets in the sail. After you route the reefing line a few times it is as easy as any other way.
For a sail that only has the second reef point I think three slugs could be spaced below the reef point to accomplish the same thing.