Drutex offers for their windows hidden hinges meaning that the hinge is hidden in the rebate clearance (gap) between the sash and the frame. Thus, it cannot be seen when the window is closed. As a result, the windows look slender and more elegant , and it is also much easier to keep them clean. The use of hidden hinges increases the thermal and acoustic insulation of windows . This is due to the lack of gaps in the seal used around the perimeter of the window. Additional advantages of windows with hidden hinges are increased resistance to burglary, ease of assembly and disassembly and the fact that they do not close by themselves.