RUB n.
obstruction, an impediment; especially, a difficulty or obstruction hard to overcome; a pinch. Every rub is smoothed on our way. Shak. To sleep, perchance to dream; ay, there's the rub. Shak. Upon this rub, the English ambassadors thought fit to demur. Hayward. One knows not, certainly, what other rubs might have been…
RULE n.
a graduated bar of wood, ivory, metal, or the like, which is usually marked so as to show inches and fractions of an inch, and jointed so that it may be folded compactly. A judicious artist will use his eye, but he will trust only to his rule. South.