This instructable covers how to make sturdy frames, specifically focusing on those annoying center bars that do not have a good place to put screws. Such an example is shown above: the first image shows a set of completed platforms that are quite sturdy enough to have multiple people jump up and down on, the second image is computer generated showing a simple frame, anthe third is a real world example of a basic frame built at the Theatre in the Park in KC.
Step 1: How to Put in Every Other Bar
A tip: be sure to measure how far from the edge the middle board is on either side and line it up proper, if it is the same distance it should pull the frame into square with far less effort on your part.
Step 2: How Not to Put in the Middle Bar
The solution can be seen in the next step.
Step 3: How to Put in the Middle Board
Putting screws in from the opposite side is easier than toe-nailing as it requires no pre-drilling and should not split either board if you aim the screw properly.