The 1960-66 Chevy C10 pickup came standard with a small rear window at the back of the cab. However, buyers who wanted improved visibility and a more "open" appearance could select a big window as an optional upgrade. For big-window trucks, the GM assembly line stamped a larger hole in the outside of the cab and welded on a matching interior window panel before installing weatherstrip and glass. Today, many C10 owners choose to upgrade their small window trucks with a big window conversion. Old Anvil Speed Shop recently published a video that shows each step of the process.