Bend Aluminum Trim to a Crisp Line With a Knife Score and a Block

The Problem

Bending aluminum trim coil in place — capping a fascia board with the soffit already up — means folding sheet metal to a straight, crisp line without a brake. Freehand bends come out wavy, and scoring too aggressively snaps the sheet in half instead of folding it.

The Technique

1. Measure and mark the bend line — the creator marks his a little over an inch in from the edge for the return he's forming.
2. Lay a straight block on the line and score along it with a utility knife: two or three light passes. A single hard score cuts too deep and the sheet snaps off at the line instead of bending.
3. Reach under the free edge and fold it up against the block, using the block as the brake.
4. Over-bend slightly past your target angle, then let it back. The over-bend is what sets the crease sharp — a fold taken only to the target angle stays soft and rounded.