The Yale 8K101 window lock is probably the best selling retrofit window lock on the market. It is simple and easy to fit and to operate. To match in with the window finish, Yale 8K101 locks have a white painted finish. They are available packaged in packs of four locks and 1 key. Lock Fitting Instructions Yale 8K101 window locks are suitable for outward opening windows and are supplied complete with all fixings, full fitting instructions and a key when purchased in the multiple packs. To install you require a bradawl, pozidrive screwdriver, pencil and ruler.