Ruth Fenner's workshop in Brackenfold made folding chairs for halls, chapels and rooms that served several purposes in a single day. The chairs had to be inexpensive, stack closely and survive being opened by people who were already holding something else. Elegance was welcome, provided it did not interfere with those requirements.
The difficulty lay in the joint beneath the seat. An ordinary arrangement could catch a sleeve or demand a second hand at precisely the wrong moment. Fenner produced a pair of linked hinges that guided the legs into position together. She tested the earliest examples on chairs returned for repair, so the new mechanism appeared beneath thoroughly familiar seats.
The improvement was first noticed by caretakers. It shortened the work of setting out a room and made the final row less likely to contain a reluctant chair. Orders began to specify the new joint without changing the rest of the design. Fenner retained the original seat dimensions because customers preferred to mix new chairs with old ones.
Several versions survive in workshop drawings. The differences are small: a wider plate, a rounded edge, an extra allowance for paint. They suggest refinement through ordinary use rather than a single perfect invention. One example bears marks where a user had made an adjustment with a file, apparently before deciding whether to send it back.
The double hinge never transformed the appearance of a room. Its contribution was felt at the beginning and end of gatherings, when chairs arrived and disappeared with less effort. It belongs to the history of inventions whose success is measured partly by how quickly people cease to notice the problem they solved.