Abstract: Guard apparatus for a window or the like in a building characterized by a guard element that is hingedly mounted to a wall adjacent the window and adapted to prevent entry into the window from the exterior and having a releasable fastener that is releasable interiorly of the building without tools to allow emergency egress through the window but resists force exteriorly of the building. The releasable fastener has a lock housing that is inaccessible from outside the building when the lock bar on the guard element is inserted into its normal latched position. Also disclosed are specific structural details and preferred embodiments of the releasable fastener.