So lots of Foamy-group therapy making rounds these days! What about some Balsa talk.

I have been tracking this wonderful Magnetic Wing assembly (even Fuse) Jig by Great Planes for the past few days:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXK337&P=7

The kit is composed of a Metallic (iron) board with grind lines and set of square magnets sandwiched between steel plates.  

Some of the live (and advanced) usage of the board:
http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/tools/magnetic_building_board/building_with_magnets.htm

Since shipping the Jig would be totally uneconomical, I have been figuring out how to build one indegeneously:

1. Metallic Board:
Alternative : White Board Which can hold Duster with magnets. Cost : Rs 190-225 /Sq Feet (I intend to have a 18"x40" board.

2. Magnets:
Though I have seen Square magnets  in SP Road Banagalore,they neither have hole in the center nor come with metallic plates.

Magnetsource.com has been selling exactly similar magnets what what originally seems to used as Latch Magnets.

http://www.magnetsource.com/airfieldmodels/

Has any one used or seen magnets like these in Hardware stores ?

Check out at GoodWill, SP road.
They do have a collection of button, square, bar and polo type magnets.
Not sure about zinc sandwich. But worth a try.