A permanent guard, railing, balustrade, gate, or infill system in which glass or another glazing material is a major structural or protective component.
Melanie Mü · Image source · CC BY-SA 4.0 · Image source · License
Meaning and boundaries
It is not ordinary vertical vision glass; required performance can include static strength, impact resistance, post-breakage behavior, support, handrail, edge, and code criteria.
Why it matters in glass restoration
Damage, edge condition, holes, clamps, interlayer, remaining thickness, surface flaws, and post-breakage design make restoration an engineering-referral decision.