and was hired by the Columbia Paper Bag Company. She noticed that the envelope-shaped machine-made paper bags they produced were weak and narrow, and could not stand on their bases. They were also poorly suited to bulky items, such as groceries and hardware goods. Machines for producing these envelope-style bags were the subject of three patents issued to Francis Wolle in 1852, 1855, and 1858. Flat-bottomed paper bags, which were sturdier and more useful, were expensively made by hand. Such flat-bottomed bags were already in general use in Britain since at least the 1840s, and improvements to hand-production techniques occurred during the 1850s. For example, a patent was awarded to James Baldwin of Birmingham in 1853 for semi-mechanized apparatus to use in the making of flat-bottomed paper bags. However, thinking to more fully automate the process, in 1868 Knight invented a machine that cut, folded, and glued paper to form the flat-bottomed brown paper bags familiar to shoppers today. This machine enabled the mass manufacture of flat-bottomed bags, much increasing the speed of production. Knight built a wooden prototype of the device, but needed a working iron model to apply for a patent. Charles Annan (or Anan), a machinist who visited the machine shop where Knight's iron model was being built, stole her design and patented it first. When Knight attempted to patent her work, she discovered Annan's patent and filed a patent interference lawsuit in the fall of 1870. Annan argued that "she could not possibly understand the mechanical complexities of the machine", possibly exploiting prejudice against women, and/or that his was a different machine (likely on the basis of details he had misremembered), and that she had not succeeded in creating a working machine. Some authors, such as Ryan Smith of the Smithsonian Magazine, state Annan argued no woman could have designed the machine, though according to Michael Abrams of the American Society of Mechanical Engineers, this is a modern exaggeration of Annan's sole argument that his was a different machine. Knight responded with copious evidence in the form of meticulous hand-drawn blueprints, journals, and models, and a number of witnesses who testified that she had been making drawings and models beginning in 1867. She spent the then-large sum of $100 () per day in legal costs for the 16-day hearing, which resulted in victory. She received her patent in 1871. For her invention of the paper bag