Does the following situation sound familiar to you? Monday morning - you leave home in a hurry. Just as you’ve closed the door you begin to wonder, ”Did I close all the windows in case it rains? Did I remember to close the French doors to the patio last night or are they only tilted – an open invitation to intruders?” In order to be sure, the only thing to do is to open the door, go back inside and check each window upstairs and downstairs to make sure you haven’t forgotten one. Wouldn’t it be more assuring if, before you left the house, you could check at a glance whether all windows were closed or not? | 
