CONSERVATION OF TIMBER SASHAND CASEWINDOWS
At Hill House, Mackintosh used an innovative method for opening sashes similar to a type designed by the National 45 Accident Prevention Window Company. Both sashes may pivot about the horizontal axis for ventilation as well as hang on cord, a feature made possible by the stile being of two sections, the external one counterbalanced, the inner glazedframe fixed to it. When the inner pivoting sash is fixed closed the whole slides as normal. (Middleton's 'Modem Buildings'. 1911)