The Historic One Lite (HOL) series is designed to be “invisible”, - when painted the same color as the existing sash. All existing sash should be operable, to permit removal and/or cleaning from the interior. There is no hardware on the exterior. Typically, one or two panels are removable from the interior, and are secured by perimeter clips.
The Operable Historic One Lite (HOL-OP) series has the same "invisible" appearance as the (HOL) units, but the bottom sash is operable and removable. It also has a year-round screen.
