Today’s invention is a flexible, cheap way to make large-scale written notices.
Units such as those on the left of the diagram can be attached to a pegboard-type background in a variety of layouts (including that of the seven-segment arrangement shown on the right).
A wire, cable or tube is looped around these units, either through the hidden or visible side of each.
This allows words to be spelled out using a continuous section of high contrast rope etc. (much more convenient than searching in a box of preformed characters for that missing ‘X’).