Some people believe that Darwin's teory of evolution of living organisms is one of the major corner stones of human civilisation. Richard Dawkins went even further and defined a "meme", the generalization of the gene, as the driving force of the evolution of morality in human society.
In this post we go a few steps back and consider the evolution of non-living things - namely screwdrivers. The evolutionary trend is - as should be expected from this blog - towards minimizing weight and size and maximizing simplicity. The first three screw drivers from the top in the picture need no further explanation. The fourth screwdriver is part of a multitool that was destined to be cut along the red line (reducing its weight to 15 g), but luckily it was spared that miserable destiny by the following consideration.
The fifth "screw driver" is actually a steel washer with the diameter 25 mm and thickness 1 mm. I filed it at the point A to produce a short flat part (not clearly visible in the picture) which acts as a flat screw driver. To be honest, this flat part is likely not even necessary. It works well with both flat and cross screw heads.
The cut in the washer at the point B serves a totaly different purpose: it is used when trueing a bicycle wheel with bladed spokes (Mavic Ksyrium wheels for example) to hold the spoke and prevent it from turning. This cut thus makes this washer-screwdriver a multitool - with 3 g probably the world's lightest bicycle multitool.
