Statistics show that 34% of burglars enter through opened windows because people are in the habit of opening windows to ventilate the home. Current sensors only detect on/off status, which doesn't help much when users open their windows a little. This device from Leedarson provides an innovative solution to maintain detection even after windows are pushed open slightly. Moreover, the multi-stage base suits various height differences between doors and frames. In summary, it lets people ventilate their homes safely.