Sure Key / Key

Nowadays, more and more people could be forgetful due to the elder age or the pressure of life, from time to time, people may forget whether they have locked the door or not. The SURE KEY with mechanical structure can help you ensure the door is locked!
Insert the key when you lock the door,the sheet metal will unlock the indicator when it's pressed. Rotate the key, the indicator will point to the the LOCKED or NOT icon.The principle is the same when you open the door.