A window with two sashes, upper and lower, that slide vertically past each other. The upper sash and lowere sash meet at the center when closed, this is known as the "meeting" or "check rail".


The upper sash is stopped in from the exterior by what is called the "exterior stop", the upper and interior sashes are separated by what is called a "parting stop". The sashes are supported and assisted in operation by either the older "weight and chain" system or the newer spiral or pulley balances.

The newer balances allow for the sash to tilt in to be cleaned from theinterior of the house.


For more information see "custom window".