A trickle vent is a very small^[opening in a window or other building envelope component to allow small amounts of ventilation in spaces intended to be naturally ventilated when major elements of the design - windows, doors, etc., are otherwise closed.

One of the most distinct features of the timber sash window is the sash horn. In the past, sash horns were an inseparable part of sash windows, which made them one of the most telling points of timber sash windows. They also served a practical purpose by strengthening the mortice and tenon joints of the window. This would ensure that the sashes of the window wouldn't be opened too far.