Abstract: A window guard for double-hung sash and window which is laterally and vertically adjustable to adjust to windows of different dimensions and which is cooperatively proportioned and related with a related window structure whereby the inner lower sash and the upper outer sash of the window structure are shiftably to afford ventilation through the upper and lower portion of the window structure and which prevents ingress and egress of unauthorized persons through the window structure. A guard structure of the character referred to having novel anchoring means and novel locking means to secure the guard in a related window structure.