There is a bolt keep on my UPVC casement window that i was replacing (it was a keep in the middle of the sash that a middle bolt slots into when the window is shut but i think that the middle bolt remains static) when another person shut the window with no middle bolt keep , the espag handle operates both side bolts and im pretty sure that the side bolts are not jammed. When i push on the window, it opens about 3mm then gets stuck, although it sounds as if something near the hinge is jamming the sash, whats the best way to get around this? 
