| 摘要 |
<p>The barrier fitted to a window, or esp. a door, enables the occupant to open it slightly, to establish identity of caller, before opening wide. It has an arm with one end swivelling on one fitting, and with a slot with a cutout, next to the axis, for a lug on a second fitting. This has a narrow part for the slot. The base piece of the lug is designed to be enclosed by the edges of this cutout (5), in one blocking position. In a second blocking position it is enclosed by the edges of a second cutout (10), when the arm (1) has slid along the slot (4). This cutout is sited at the slot end furthest from the axis (3).</p> |
