Slider windows and double-hungs have a lot in common. In fact, a slider window is essentially a traditional double-hung lain on its side! Both windows have two operable sashes designed to move smoothly season after season, safety stops and locking hardware that provide security, and swing-in or tilt-in sashes (for slider and double-hung, respectively) that make cleaning a breeze. The main difference is that slider windows are designed for window openings that are wider than they are tall; double-hungs are ideal for the reverse.