$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.10
\begin{equation} \begin{gathered}\label{equation:relative-outer-horn-filling2} \xymatrix@R =50pt@C=50pt{ \operatorname{Tw}(\Lambda ^{n}_{0}) \ar [r]^-{ F_0 } \ar [d] & \operatorname{\mathcal{C}}\ar [d]^{ U } \\ \operatorname{Tw}(\Delta ^ n) \ar [r]^-{ \overline{F} } \ar@ {-->}[ur] & \operatorname{\mathcal{D}}. } \end{gathered} \end{equation}