 The close match of the 3D structures shows that the 2-fragment S system does indeed fold to the active form ().In 1968, while on sabbatical with David Phillips at Oxford, Richards developed a large optical comparator device called a "Richards' box" (or "Fred's Folly") which enabled crystallographers to build physical models of protein structures by viewing the stacked sheets of electron density through a half-silvered mirror (see photo).Once the Folly had been constructed, he built an all-atom brass model of RNase S quite rapidly.