Please excuse my ignorance but what are the wiggly lines on this picture?
These lines are part of FontLab True Type hinting; Type 1 PostScript hinting does not have such hinting specialized commands.
Although FontLab does not offer full TrueType hinting options, it provides a high level aproximation.
In TrueType, hinting is a bit more complex and somewhat time consuming task: it supposes programming the glyph outline for working at specific sizes, so you can create the "perfect character" that looks well at every size: one can align points, interpolate, move parts of an otuline with a middle delta, or a single point with a final delta, set single or double links, and so on.
I don't know what FL version are you using, but these lines seem to me custom links.
I'll note that given the lack of points at extrema, and the relatively arbitrary positions of the ones that are there, the hinting isn't going to do a very accurate job of controlling stem widths and counter size. It's also odd that there is no hint controlling the thickness of the right stem.
What you have here is a mess. It is not TrueType hinting that is being displayed, but some badly constructed links on a Postscript outline (links, which FontLab turns into hints). The "wiggly" lines show the dimension of the link. There is no link controlling the left stem. The first link is related to the counter, then you have a link controlling the middle stem, then the counter, and then the right stem. As Tom points out, there are few points placed on the extrema, which is the basis for the failure of this hinting routine.
These are Links, which FontLab generates as hints in PS fonts or which you can convert to Hints within FontLab. The difference between Links and Hints within the FL glyph editing window is that Links always are connected to specific outline nodes, while Hints define zones whose edges may or may not align to nodes. Links are useful sometimes, especially when editing Multiple Master outlines, because the Links move with the nodes whereas Hints are static. However, Links can also be tricky because if you delete a node to which a Link is attached, the Link detaches and, depending on the circumstances, either jumps to a nearby node, becomes a ghost Link (like a PS ghost hint; only for y-direction links), or disappears.
I've seen such wiggly lines in the past. Most often they appear for me when trying to blend in FontLab 4.6 not-that-well-hinted fonts into one MM master. FontLab 5.x is waaay better in the MM blend process and does not create such mess...
Oops, I just noticed I wrote "right stem" above when I meant left stem. Sorry if that caused any confusion.
Thank you for all the responses. I'm not really sure I understand much about hinting or links (and certainly not deltas!), but I gather I need to either put the nodes at the extrema or do manual hinting, I think?
You need to at least do the first; see how happy you are with the on-screen rendering before you decide to attempt the second.
Be smart – run the Adobe Autohinter on your PS-outlines. Works very well.
Yes, as long as you have PS-style outlines, and they are well made, and you set your global values correctly, the Adobe autohinter is very nice.