Bulk materials — cabling, piping, board, hardware, paint, adhesives and fasteners — are bought against a take-off schedule from manufacturers and authorised distributors.
Door and glass systems are sourced as complete systems including hardware, so responsibility for fit and function sits with one supplier rather than being split.
Direct manufacturer supply is used where it is genuinely available for the category and volume. Where a brand supplies only through authorised partners, we buy that route to protect warranty and benchmark it so the difference is visible.