Lately (11/08), I have seen on the various forums lots of methods and equipment designed to join top and back plates together. Thanks to Mario Proulx who shared this idea, I have been using nothing more than masking tape to join tops and backs over at least the last fifty guitars I have constructed. No jigging of any kind. The method takes advantage of one of the inherent properties of hide glue, i.e., that hide glue will actually pull together a well made glue joint as it dries. Therefore, this method requires the use of hot hide glue to join the plates. Here is how it is done:

Make sure it has acclimated to your shop. I don't use any wood for at least a year after it is stored in my shop.

Join the two pieces together with your jointer. Make sure you join both pieces at the same time to counter any possibility that your equipment is not at exactly 90 degrees.

After joining, hold the plates together with a strong light source behind them. If the plate is not joined tightly you will see light coming through the joint. Work on the joint until there is no light.

Lay your joined pieces on top of a piece of wax paper. Get the heavy duty masking tape (Stewart-MacDonald).

Using the heavy duty masking tape, apply five strips equidistant down the joint pulling the joint together tightly.

This time apply the masking tape to one plate only, folding over the excess tape.

Get your hide glue ready to use. Make a "teepee" out of your joined plates.

Place a couple of weights on top of the plate to hold both sides down and even with each other. Let dry overnight. Hide glue will draw the joint together tightly. If you have done it correctly you will have, literally, no visible seam at the joint so make sure that you have marked, in some way, your center seam or it will disappear after gluing!