I thought mining
In winter the Netherlands in the past. Heavy snow so much that all the parts and all areas of the city were covered with snow. But the authorities of the Netherlands have taken fright. When the roof of a house, there are no marks on the snow after all. It marks the appearance on the roof, it looks very unusual and noticeable.
When officials investigated, they found. Indeed, homeowners were "growing marijuana" inside the home theater as ever, which is more than the law requires that the Netherlands can grow up to 5 above.
And hence The heat from a lamp used to grow marijuana, so that the light from the accumulation on the roof. When the snow falls, it melts away. Become evidence which led to the arrest of the best.