A building product manufacturer wanted me to write a guide spec that said, "No substitutions allowed."

I replied that, if they REALLY think the architect will reject substitutions, their guide specification needs only three lines:

Part 1 - General: Submit manufacturer's product data and installation instructions.

Part 2 - Products: Provide: Model XYZ with options ABC and LMN as manufactured by YourNameHere, Inc.

Part 3 - Installation: Comply with manufacturer's instructions.

END OF SECTION