In this code, I put "PointSize[0]" (or [-1])
NumberLinePlot[{Sin[x] < 0, Sin[x] >= 0}, {x, 0, 13}, PlotStyle -> {Directive[Thickness[0.001], Red, CapForm["Butt"], PointSize[0]], Directive[Thickness[0.001], CapForm["Butt"], Black, Opacity[100], PointSize[0]]}]
but I get this plot
As can be seen, those circles still exist (cf. magnified part). How can I get rid of these circles and have only line segments?