These are fitted to windows to restrict the amount it will open, usually above ground level to avoid persons falling out. These restrictors come in many different styles and can be fitted to most types of windows.
These are black (sometimes white), which are seem round the perimeter of the glass on the inside and outside of the window. These sometimes perish or shrink and should be replaced to avoid drafts and water penetration.
If a window is not closing properly, either catching, or rubbing, this can cause damage to frame, locks and handles. This should be rectified by re-glazing and packing the glass correctly.
This is where the handle back has broken away from the main body that is screwed to the frame or the inner spindle has broken causing the handle to spin or fall off.
This is where water has penetrated the glass sealed unit causing it to mist up and show condensation on the inside. Sometimes the inside turns white and shows unsightly water stains/marks.