Design Tool-Free Modular Connection System

I need a mechanical design to connect modular boxes. Each box weighs about 15kg, and can connect up to 4 boxes on its sides. Dimensions are 25 cm x 50 cm.

Requirements:
- Boxes made of metal
- Connection using clips or latches
- Stability against vibrations and weather

Ideal Skills and Experience:
- Mechanical design expertise
- Experience with metal fabrication
- Knowledge of vibration resistance techniques
- Proficient in designing tool-free assembly systems