The reason it is called a gaff rig, after all, is the gaff itself.

The page on the Great Peak Halyard Controversy includes more about attaching the peak halyard to the gaff, but for the purposes of this page, I want to focus on the construction of the gaff itself.

Below are two illustrations of the gaff attachment to the mast. One is from Roger C. Taylor's excellent Knowing the Ropes, and the other from John Leather's Gaff Rig Handbook. I've seen a few variations on this theme, but all include the gaff, the gaff jaws, and the line from jaw to jaw to keep the gaff on the mast (in this drawing, the line has parrel beads on it.)

The parrel beads and tumbler are not always seen on small craft, although you do need a parrel line to keep the jaws on the mast (at least, that's what all the texts tell you ... I sailed for three weekends without on ... having had to cut it when I had it trapped in the mast tabernacle. While the gaff stayed where it should, I was sailing in light airs, so I never put the accepted wisdom to the ultimate test.) The stresses are smaller on sails under 200 square feet, and the tumbler is not needed to spread out the stresses on a larger portion of the mast. Usually, the jaws are either greased or lined with leather (or both) to prevent scoring the mast.

It is worth noting the strop around the gaff for the throat halyard attachment in Leather's illustration on the right. Strops and lanyards have the advantage of being relatively inexpensive (in comparison to stainless steel). And, they "compress" better if you have a folding mast.

On my Weekender, I used a tumbler because of my hollow mast; I was concerned that even the small stresses might be too much for it. The tumbler (sometimes called the "chip") is mounted on a threaded brass rod, with brass nuts jammed against the tumbler to give it some stiffness. The bottom picture shows this assembly in a little more detail.

Gaffs are often constructed of solid wood. You can make a hollow gaff to save some weight aloft. The gaff I made for my Weekender was made using the "bird's mouth" method, and is hollow. The weight saved might not be that much though; a 1 1/2" round "dowel" from the lumber yard doesn't feel that much lighter. But with larger gaffs, reducing weight aloft is always a good idea.

The gaff jaws on most craft can be straight. Sometimes you see a gentle upswept curve to the jaws, and sometimes it is exaggerated to a wide sweep. Unless the gaff is going to be peaked up quite high, straight is fine. And it is easier to build.