Prehung exterior door units are fastened in place using which type of finishing nails?

The use of 16d finishing nails for fastening prehung exterior door units is a common practice due to their size and strength, which provides adequate support for the weight and structure of the door. These nails are long enough to penetrate through the door frame and into the wall framing, ensuring a secure installation that can withstand the forces exerted on exterior doors, such as wind pressure and frequent use.

Using finishing nails allows for a clean finish, as they can be slightly countersunk and concealed with wood filler, maintaining the aesthetic appeal of the door frame. In contrast, nails that are shorter or less robust, such as 8d, 10d, or 12d nails, may not provide the necessary holding power for exterior applications where durability and security are critical. Therefore, 16d nails are preferred for their balance of length and strength, making them the most suitable choice for this task.