The Yale 8K101 lock is surface fixed onto the window section and is locked around the frame fixed staple by use of the key. A clenching action helps to pull the window to the frame for added security and will also help to reduce draughts. The Yale 8K101 are suitable for hinged timber casement windows and can easy be fitted in minutes. 2 x Additional Keys Only for 8K101 Window Latch Lock. The additional keys are ideal to stored in a safe place in case of misplacement of the original key.