0framistan 8 years ago The most important tool is just your imagination. This will help you design something that is within your budget, abilities, and tools available. For example: The front door of my house is a solar collector without building anything! My house faces SOUTH so the door is aligned right. The OUTER door is a big glass panel, and the INNER door is BLACK METAL. When the winter sun shines on our door, we can't hardly touch the doorknob because it is SO HOT. No tools required at all.