Telco Upper Biparting Doors 

Telco upper or “Telescopic upper” doors consist of two shorter upper panels and a single lower panel. In this situation, the lower panel will be constructed with a wider trucking sill. This is called an extended sill. This extended sill will need to be included on all doors in the same line.
Telco Uppers are used when there is minimal overhead space at the top floor.