How it works on my 23
With the mast laying out over the bow and the front pin on the step plate in place the boom is installed. The topping lift is attached, as are the upper shrouds and the mainsheet. The lines you found are attached with the D shackles attached to the triangular plates on the shrouds. the rope ends are tied to the clew (aft) end of the boom. Thus the boom is held in place at right angles to the mast - i.e. mast laying down and boom pointing skyward.Then, by pulling in on the mainsheet the mast rises. Make sure the forestay is attached. I know this is the way the PO of "Heron" was able to raise the mast alone. On a 23 it's easier to just lift the mast by hand, especially if there are two pairs of hands available.Hope this is clear enough.Chris