A jib is a triangular sail set between the foremast and the bowsprit (or, more properly, the jibboom, which is an outward extension of the bowsprit). It made its appearance late in the seventeenth century. Being set so far forward, it was able to exert enormous leverage in turning the ship around. By the mid-eighteenth century (if not a little earlier), somebody figured out that the amount of force it contributed to the turning motion of the ship could be adjusted by changing the position of the forward bottom corner (the “tack”) along the length of the jibboom. The farther out along the jibboom the tack was secured, the more effect a wind blowing from abeam into the jib would have on the ship’s tendency to turn downwind. So somebody invented the jib traveler.
The jib traveler was a ring, made initially of rope and later of iron, that slid along the jibboom. It was controlled by the outhauler (a line running from the traveler to either a block at the end of the jibboom or a sheave in the end of it) and the inhauler (a line running from the traveler to the forecastle deck). Hauling the outhauler and slacking off the inhauler made the traveler move out along the jibboom; the reverse made it move in.
Another characteristic of this arrangement was that the jibstay (the line that ran from the jibboom to the foremast, and to which the long side of the sail was secured) had to change in length when the traveler was heaved along the jibboom. Hooked to the traveler was a block, through which the jibstay passed. (When the iron traveler was introduced, it usually had a roller built into it for the jibstay.) The end of the jibstay was then taken inboard to the forecastle deck; in a big ship it usually had a tackle rigged to its inboard end for the purpose of hauling it taut.
The other lines associated with the jib in those days included the halyard (running from the peak of the sail, alongside the jibstay to the masthead, then through a block and down to the deck), the downhauler (running from the peak of the sail down to a small block on the traveler, then inboard to the forecastle), and a pair of sheets - one leading to each side of the ship, for use when the ship was on the port and starboard tacks.
Fairly early in the nineteenth century this system got simplified a bit, with the elimination of the traveler. From that point onward the jibstay was rigged permanently between the masthead and the jibboom, and the inhauler and outhauler disappeared.
From Spelunko’s standpoint, the good news about all this is that it’s irrelevant. The Santa Maria sank long before the jib was invented, and the Pamir’s jibs were rigged with permanent stays.
Regarding jeers - in the late eighteenth and early nineteenth centuries they generally were part of the permanent standing rigging. The primary purpose of the lifts in that period was not to support the yards but to make it possible to tilt them in the vertical plane. In a big warship like the Victory there was a relatively fail-safe system of keeping the lower yards aloft, in case any of the components were damaged by shot. The jeers hauled the yard up in the first place, and generally stayed in place. (The jeer blocks for the mainyard probably were the biggest blocks in the ship.) Once the yard was up, it was secured to the mast by the “truss,” a fairly simple system of heavy ropes that could be slacked off a bit, so the yard could swing a little more when the ship was working to windward. And a heavy, parcelled-and-served line called a “sling” was rigged between the yard and the lower cap (usually with a pair of bullseyes) to hold the yard up. If either the sling or the jeers got shot away, the yard (theoretically at least) would stay aloft. During the process of “clearing for action,” the rope slings sometimes were replaced with heavy chains for extra insurance. If either the fore- or mainyard ever came down, the result would be disastrous.
All this is hard to describe verbally - and probably harder to understand. The drawings in the Longridge book make it all pretty simple.
Early in the old movie “Captain Horatio Hornblower” (the one with Gregory Peck), a wind comes up to rescue Hornblower’s ship from a long period of doldrums. Somebody yells, quite enthusiastically, “Away the mainyard!” That line always gives me a laugh. (If the order were carried out, most of the ship’s rigging would collapse in a matter of seconds.) Another of my favorites is Charles Laughton’s famous line to Clark Gable in the original “Mutiny On the Bounty”: “Mr. Christian, I won’t rest until I see you hanging from the highest yardarm in the British navy!” The real Captain Bligh surely would have known that (assuming the lifts of the ship in question were properly rigged), there were two highest yardarms in the British navy: one at each end of the highest yard in the British navy.
Spelunko - That’s a pretty good list of books. One word of warning about the Davis one: it’s full of good information, but it was published in the 1920s. Don’t expect the techniques described in it to be up to date. I’d recommend two others (both paperbacks, and not terribly expensive): Wolfram zu Mondfelt’s Historic Ship Models and George Campbell’s The Neophyte Shipmodeler’s Jackstay.