Here are schematics for a standard Strat™ style guitar before and after shielding:

Stock Stratocaster Wiring

Shielded Stratocaster Wiring

Notice that there is not a great deal of difference in the electrical schematics. However, to get from the first picture to the second quite a few ground wires have to be moved. Also, even though the difference between the schematics seems minor, the amount of noise reduction achieved with the circuit in the second diagram can be amazing. Click here to see "non-artist's renderings" of how the two circuits look (non-scale rear views of pickguard).