Sentence:  the sides of windows, where the jamb makes an <WSD>elbow</WSD> with the window back 
Meaning of the word marked with <WSD> tags:  Any turn or bend like that of the elbow, in a wall, building, coastline, etc.; an angular or jointed part of any structure, such as the raised arm of a chair or sofa, or a short pipe fitting, turning at an angle or bent.