What You Need :A Wooden Box (Ask in a tobacconists / cigar shop. They usually have empty ones. I make a donation to charity, and take as many as I can carry ! - Junk shops / Charity shops / friends...)
A Piece of Wood (Aprox. 3' X 2" X 1") - I've used legs from easels, furniture, floor timber, walking sticks, hockey sticks... It's handy if you can get them sawn and planed to size (Cheers Simon at WASPS). Hardwood like oak, cherry, wenge is best, as it won't bend.
Some guitar strings. (Top 4 or bottom 4 work...Try other combinations too.)
Some guitar tuning pegs
Wood / metal / bone / plastic... for a 'nut' and a 'bridge'
Piezo transducer pick-up (£1.09 each from MAPLINS or similar store)
Mono Guitar socket
Ferrules (to hold the tuners)
Wood for fretboard
Clamps (with cardboard to protect wood)
Sandpaper / Rotary Sander
Power Drill (With Assorted Bits)
Soldering Iron & Solder
Wooden Block (Useful for drilling to prevent wood splinters and for holding components when soldering.)
* If you are adding frets, a template is very helpful for getting the position right. These can be found at the Handmade Music Clubhouse site : Handmade Music Clubhouse or you can make a template from any guitar or banjo.
There is a useful link in my step-by;step building guide.