$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.55
\begin{equation} \begin{gathered}\label{equation:restriction-to-endpoint-diagram} \xymatrix@R =50pt@C=50pt{ \operatorname{Fun}( \Delta ^1, \operatorname{\mathcal{C}})^{\simeq } \ar [r]^-{\theta } \ar [d] & \operatorname{Fun}( \Delta ^1, \operatorname{\mathcal{D}})^{\simeq } \ar [d] \\ \operatorname{Fun}( \operatorname{\partial \Delta }^1, \operatorname{\mathcal{C}})^{\simeq } \ar [r]^-{\theta _0} & \operatorname{Fun}( \operatorname{\partial \Delta }^1, \operatorname{\mathcal{D}})^{\simeq },} \end{gathered} \end{equation}