Super Sill WindowSill Shelf (2002) Super sills is a windowsill extender for anything you want to put on your windowsill Super Sills expands the standard 2 1/2" windowsill to 10 X 24 window shelf It holds over 30 LB level and with the deep lip it can hold one quart of liquid Unlike other windowsill shelves super sills was designed not to harm your windowsill To clean or move it to a different window just tilt up the front and pull the legs back and it's off Super Sills work with double & single hung windows with more than a 1/8 gap between the window sash and stool It does not work with slider, casement, or certain Vinyl windows