4(d). Mechanical model: a working device, approved first

Warning. THIS IS THE ONLY OPTION WITH AN APPROVAL IN IT, AND THE APPROVAL COMES FIRST. The requirement reads: once your design is approved by your counselor, build a working physical model. That is an approval on the design, before the build, and it cannot be granted retrospectively. A device built over a weekend and shown afterwards has skipped a step the badge asks for. Two other things are particular to this option. It is the only one of the five with NO scale imposed, which makes it the route to take if the arithmetic of scale is the part you were dreading. And it is the only one whose wording requires the model to be WORKING, so at least two of the six simple machines have to actually do something.