Single slider windows operate horizontally (side to side).One sash does not open and the other sash moves. Included is a screen that covers half the window. The moveable sash moves sideways and can tilt into the room for easy cleaning. Added features such as extra weather-stripping and a sash encapsulated into the frame will ensure that drafts cannot break through. Our windows are manufactured to tight standards so that when locked, there is virtually no movement.