Stavenau worked in the Engineering Department and had designed many tools for their product line. In 1953, Truth received an order for 1,000 push bar awning window operators, a relatively cheap and very basic, unsophisticated method of opening and closing an awning window, with the disadvantage that it left a long handle protruding into the room when the window was only partially open. At that time Stavenau was completely unfamiliar with the existing window hardware, so instead of rehashing old designs he started with a clean sheet of paper and came up with a revolutionary new product. Always an original thinker, he was not burdened by how someone else had previously solved a problem, and could not overlook that basic design weakness. "I looked at it... I was not very enamored of the idea of this big bar sticking into your room it you want to open your window slightly," Stavenau later said. He took it upon himself to design a better awning window operator and came up with a revolutionary new product. The result was the lever lock operator. This piece of window hardware was soon on most of the awning windows produced in this country and led to the design of a full line of hinges, locks and operators for all kinds of windows.

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Many window manufacturers welcomed his invention as the first new piece of window hardware to come to market in 50 years. Truth Tool had made hand tools since 1914. The immediate success of the product soon led to Truth Tool Company to drop its entire line of hand tools and become exclusively a window hardware manufacturing company. It moved its operations to Owatonna in 1959.

In addition to his product design work, Stavenau is responsible for making Truth the most efficient hardware producer in the country with his innovative ideas for production and assembly fixtures. The end result of his genius is that Truth was transformed from a small, struggling hand tool company to the world’s largest producer of window hardware. By the year 2000, it employed over 1,500 people producing annual hardware sales in excess of $170 million. Truth window hardware is used throughout the world.