Remark 1.2.1.5. Let $f: S_{} \rightarrow T_{}$ be a map of simplicial sets and let $T'_{} \subseteq T_{}$ be a summand. Then the inverse image $f^{-1}( T'_{} ) \simeq S_{} \times _{ T_{} } T'_{}$ is a summand of $S_{}$.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$