Step 6: Step 4: Electrodes

Picture of Step 4: Electrodes
To make sealing washers, I cut 4 circles out of the tire inner tube, and then cut out the centres. Putting these on the outside, between the bolt head and the Perspex bottom, I bolted on the electrodes, L side facing out, so that the electrodes were as close to each other as possible. The bolt holes in the Perspex were 40mm away from each edge. There should only be washers between the bolt head and Perspex, not between nut and electrode, as this is where the electrical connection is made.
You may want to consider using inert carbon rods (which can be found inside "super heavy duty" carbon-zinc dry cells) rather than the metal bolts you have posted above. Eventually, no matter the composition of the bolts, if they are metal, the anode will corrode and wind up deposited on the cathode. This is also the reason why batteries use carbon instead (in carbon-zinc ones)- while being excellent conductors, they won't corrode.
This is not true, Carbon reacts with the oxygen being produced forming carbon dioxide,
And not all metals are reactive.