Sorry guys, I know this is a very old discussion and I am not saying I
agree with the proposition, but it caught my eye.

One thing I do know is that edible snail growers do use copper strip
to confine snails. I originally believed this was something to do with
getting a mild electric 'shock' as their slime reacts with the copper
- still do.

However, this tool thing implies either something different or a
potential electric shock biugger than I thought possible.

These guys sell copper tools and make a passing reference to snails
and slugs not liking copper.

www.implementations.co.uk/
http://www.nutec-supply.com/copper/ Not sure about this one
http://www.rittenhouse.ca/asp/product.asp?PG=1397

These people (integrated pest management I think) talk about using
copper barriers for snails.
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7427.html

Here's something else, talking this time about water snails and
effects of copper sulfate.
http://www.osti.gov/energycitations/...sti_id=5487993

http://www.usc.edu/CSSF/History/2004/Projects/J1920.pdf

Guess the thing to do would be to rope off a section of plants and
ring them with copper nails (must have the same effect as using copper
tools if there is one), and do a control with the same plants
elsewhere?

Perhaps the effect is a light electric charge in the soild if you
leave the tools sticking in the ground? One of the above mentions a
380mV charge from copper strip. Also copper fastenings on boat hulls
can rot very quick and produce a sizeable current.

Another thought - copper chloride - if there is a deterioration of the
metal into copper chloride (salts in the soil) this may trigger a
small battery action. The same chemical is used in some cheap water
activated batteries for life jacket lights. Copper chloride being one
of the battery plates.