Go Bar Deck
Stack and glue two of the pieces together and stack and glue the other four together the extra thickness is required to give the go bar deck base sufficient stiffness.
Go bar deck. By bending fiberglass or wood rods between the upper and lower decks it is easy to put pressure just about anywhere you need it. The compression bars are made from straight grained maple with a 3 16 x 3 8 cross section. A gobar clamping deck is a nifty system for clamping. Now you could just use lots and lots of expensive clamps with many cauls but most luthiers use what is called a go bar deck.
The bars worked well when left 1 2 3 4 longer than the clear distance to the upper deck. The deck is roughly 2 feet square and 2 feet tall. What you are looking at is a go bar deck sitting on the extension table of my table saw. After trying a couple of alternatives from the local big box store as well as my back yard i broke down and bought a set of 3 16 fiberglass rods for the go.
In the picture the upper transverse brace is being glued to the top of an acoustic bass guitar. Go bar deck assembly from a sheet of 3 4 plywood cut six pieces each 2 feet x 2 feet. 3 8 threaded rods were used to make the deck easy to break down and store. The basic idea is that you apply vertical pressure using rods usually fiberglass under tension.