Christian:

I routinely use a part called a "hex threaded standoff" as the legs for the corners of test boards. These are made of nylon and can be seen on this Keystone catalogue page:

http://www.keyelco.com/kec/pdfs/p48.pdf

I then use a nylon screw down through the PC board hole into the "hex threaded standoff". If you want to have a base plate then make the standoff long enough to permit the use of a short screw from either end. Here is a look at the Keystone catalogue page for nylon screws:

http://www.keyelco.com/kec/standpro/stdframe.htm

Keystone parts can be purchased at DigiKey which now has an international page at:

http://dkc1.digikey.com/uk/mkt/International.html

Michael Karas