These are 3D printed parts to enable quick and easy assembly of a particular duoband Yagi antenna, the design for which can be found [here](http://www.qsl.net/dk7zb/Duoband/duoband_2-70_2-3.htm). The design has been developed in collaboration with the amateur radio league in Nepal.
The parts enable the antenna elements to be quickly positioned on the boom without a need to measure out exactly where they should go.