Let $E$ be a cartesian fibration over $B$ such that $B$ has
binary products. A displayed object $\bar{s}\in E\Sub{s}$ is said to be a
*small separator* for $E$ when any two vertical maps $f,g:\bar{u}\to\Sub{\Idn{x}}\bar{v}\in E\Sub{x}$ are equal when they are agree on $\bar{s}$-figures in the sense of Definition 4.3·c [002I].