Install Types & Frame Profiles
Nail Fin (Nailing Flange)
A nail fin (also called a nailing flange) is a thin lip that runs around the perimeter of the window or door frame. It laps flat onto the wall sheathing so you can fasten straight through the fin into the framing studs. After the unit is screwed off, you flash over the fin with tape, then run your siding on top to lock everything in. This is the standard install for New Construction on Stick Framed walls, and in Anchor it's the only application type that pulls nail-fin screws, which are priced per linear foot around the frame.
- Install type: Nail-fin
- Best fit: New Construction, Stick Framed
- Fastening: through the fin into studs
- Pricing: nail-fin screws per linear foot
- Weather seal: flashing tape laps over the fin
- The fin sets the window plumb against the sheathing and gives a wide, even nailing surface, so the unit can't rack in the opening.
- Flashing sequence matters: sill flashing first, then jambs, then head flashing laps OVER the fin so water sheds outward, never behind it.
- Because the fin and flashing get buried under siding, this install is meant to be done before the exterior is finished, not as a swap-out later.
- In Anchor, choosing Nail-fin is what adds the per-linear-foot nail-fin screw line to the estimate, billed around the full frame perimeter (head + sill + 2 jambs).
Pros
- Strongest, most weather-tight attachment for New Construction
- Wide nailing surface keeps the unit square and rigid
- Flashing tape over the fin gives a clean drainage path
- Hides completely under siding for a finished look
Watch-outs
- New-construction only — needs exposed sheathing, not for finished walls
- Disturbs siding and flashing, so it's impractical as a replacement
- Adds the per-linear-foot nail-fin screw cost to the job
- Mistakes in flashing order can trap water behind the fin