An unusual fourfold extended dislocation node at a SixGe1−x/Si strained layer interface has been revealed using weak‐beam electron microscopy. A detailed contrast analysis shows that this node structure is the result of the constriction of Lomer–Cottrell dislocations formed by intersecting slip dislocations on {100} and {111} type planes. This mechanism necessitates the glissile behavior of dislocation nodes at the (100) epitaxial interface.