A fixed AFD (Anti-Friction Device) is a stationary low-friction surface—usually Teflon—built into the toe piece of your binding. When your boot releases sideways in a fall, it slides across this smooth surface rather than dragging against a rough platform. Unlike sliding or rotating AFDs, the fixed version doesn't move with your boot; it stays in place.
This design works perfectly if you ski in standard ISO 5355 alpine boots, which have flat, rigid soles. You'll find fixed AFDs on many entry-level to mid-range alpine bindings, and they keep things simple and reliable for traditional setups.
The catch is compatibility with GripWalk or rockered soles. Because the fixed AFD can't adjust its height or position, it may not release consistently with those thicker, curved soles. If you own GripWalk boots—or think you might switch to them—look for a binding with an adjustable sliding AFD instead. Never try to modify or lubricate a fixed AFD to make it work with incompatible boots; that can seriously compromise your release safety.