  We propose a configuration of D-branes welded by analogous orbifold operation
to be responsible for the enhancement of $SO(2N)$ gauge symmetry in type II
string compactified on the $D_n$-type singular limit of K3. Evidences are
discussed from the $D_n$-type ALE and D-manifold point of view. A subtlety
regarding the ability of seeing the enhanced $SO(2N)$ gauge symmetry
perturbatively is briefly addressed.
