Galvanized ducting buried under concrete slabs can collect water, debris or worse. There is an air duct cleaning system that not only cleans your ducts, but coats them with a waterproofing compound. This system uses your existing ductwork, so no need to install new ducts.
In cases where stud finders don't work, or if you don't have a stud detector, you can locate framing studs the old fashion way. Wall studs can be found using a nail, a hammer and a little observation.
A window box has to be properly anchored to your house. Flower boxes with soil, flowers and water can weigh hundreds of pounds. Consider a French cleat to support your window boxes. French cleats work great and are hidden.
Who should pay for construction tools and materials? If the tool is completely used up on the job, the customer should pay for it. What about a tool the spans several construction jobs?