Cork and meccano
Many years ago I bought 4 field mapper sets from Pasco. These include of 50 sheets of conductive paper and a silver pen. The silver pen is used to draw electrodes on the paper so that different fields can be investigated. The problem is that the silver pens ran out years ago making the kits not so useful. I use the cork boards when marking multiple choice tests. Put a pile on the board and pierce the correct answer with a pin, then count how many holes coincide with the ticked answers.
The other day I was thinking of a practical on fields to do with my first years. The conductive paper was the obvious choice if only I had the silver pens. eBay didn't turn up any likely looking pens so I thought I'd try an alternative way of connecting with metal strips. My first trials didn't work well but when I turned the paper over and used the side without the grid on it I got much better results. I also found that using the blunt ended banana connectors was much better than using pointed voltmeter probes.
The only problem now is that I only have 4 cork boards. Maybe I can use G clamps to press the strips onto the paper?