Protection Level

A classified threat the structure must defeat — STANAG 4569 levels for vehicles, EN 1522 FB classes for buildings.

Designs are specified against a level, not against a plate. The level fixes the projectile, velocity and range for the test, and acceptance is by firing trial on the built panel, not by material certificate alone. Because joints, mountings and overlaps are part of the panel, a design that changes the weld placement can fail a level the plate itself passes.