Never use a razor blade on tempered class it will scratch the glass.
The process to make tempered glass is to bake it. There are fine particles that settle on the surface. When you use a razor blade, it pulls out these particles and scratches the surface.
Always use 00-00 steel wool on tempered glass.
Neighbors, inspectors, architects, homeowners, subcontractors — many parties are involved and impacted by a renovation, and a good contractor can keep anyone from coming to blows. Some disputes are bound to occur, and the contractor is often the one trying to reach a resolution, because next to the homeowner the GC has the most at stake.