On a scaffold, in addition to fall protection, what protects workers BELOW from falling objects such as tools?

Explanation

The standard requires the object to be stopped: toeboards along the edge of the platform, and where material is piled higher than the toeboard, panelling or screening above it; alternatively a guardrail system with openings small enough to hold the objects, or debris nets, catch platforms or canopies, or barricading the area below so nobody can enter. Hard hats (a) are separately required for everyone exposed to overhead work, but the standard puts the object-stopping measure first and does not accept PPE in its place. A signal person (c) and tool lanyards (d) are sensible practices - the lanyard especially - and neither is what the standard specifies, nor does either address the stacked material that makes up most falling loads.