When evaluating modular furniture, prioritize structural integrity and material durability. For frames, ensure the use of kiln-dried solid wood or reinforced steel to prevent warping. For upholstered modules, a high-density foam (minimum 30kg/m³) is essential to maintain shape over time. Additionally, verify the locking mechanisms (such as alligator clips or recessed connectors) to ensure individual modules remain securely joined during use. For commercial environments, specify Martindale rub counts of 30,000+ for fabric longevity.