Here is the second of the two species of brush that I carry. I have but one of these, I carry three, or perhaps four bristle brushes (of course I have spares for each in my brush quiver) but only one little pointy brush.
This is a rigger, for many years I used sable riggers but now I am happy enough with the "golden Taklon" synthetic hair. The one I use is a #4 series 7050 script , and at present they cost 3.64.You can get them from Jerrys here.
I call all long, thin, sable- like rounds "riggers" as a convenience, however different lengths of hair or different manufacturers may actually call this sort of brush a script brush, a scriptliner or for the really whip like ones, a rigger. I believe that ship painters may have used those to paint the rigging on boats. I don't know much about ship painting, it is it's own little netherworld.
I HATE BOATS, THEY SINK.
I am particularly fussy about the condition of these brushes, because as they wear, the tips of the hair explode as they abrade to the unattractive thatched end that no longer provides a crisp line. As soon as they begin to lose their neat tip, out they go!
Don't leave a rigger behind uncleaned at the end of a painting session, if paint dries in one of these it will quickly be ruined. Even if you only clean them real well in your solvent, rather than with soap and water, make sure you never forget to put these away clean and protected in your brush quiver, wallet or pastry belt area.
The rigger is what I use to put little branches in, define the rake-boards of a house or other little details or things with man made straight lines. However! this little brush is dangerous, it tightens up and can rob your work of painterlyness . It's overuse can rapidly give your painting a brittle, seized up and crabbed look, so use it gingerly.
OVERUSE OF THE RIGGER BRUSH WILL GIVE YOUR PAINTINGS RIGGERMORTIS!
Say, that might make a dandy neck tattoo!.