The horizontal side slider is probably the simplest and yet most versatile window available. Installed "regular", "reverse", or continuous track multiple vent. At the touch of a finger these full length sliders will glide open or closed...or lightly lift out for easy cleaning or storage.When open, these sliders expose 50% of screened area for ventilation. Vents can also be removed and stored to allow a 100% opening. The PGT four track horizontal side slider enables you to obtain up to 75% ventilation of an entire screen wall. This continuous track unit is normally installed in a "reverse" fashion. Often used to separate the pool area from the patio, it can provide a maximum access to the pool when open, yet keep the cool winter wind out when closed. Threshold is available at an extra charge. Unit can be ordered sill without a flange at no extra charge. Normally installed with four vents, the four track horizontal side slider can be ordered with as many vents as needed to cover any wall area.