I have seen them in hospital windows. One side is a long metal piece on the frame & the window there is the small piece which has the key which turns to meet the side of the window frame so you can open the window for ventilation in any length. I like to know where I can buy these locks. The window is a mental double hung style which replaced the old wooden windows. I don't want to get robbed. It is about a foot long or so lock. The hospital wouldn't tell me where to buy it.