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
To make framing simple as many bars as possible are screwed in as shown above, generally every other bar. The screws run through the vertical bar into the horizontal, two to hold the board in place. Unfortunately this leaves the third bar in an odd predicament, you cannot screw it in like the boards to either side.
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 obvious solution would be to toenail the middle board in as shown in the graphic above. This is not very structurally sound as the screw has less than an inch of wood in the middle board to hold onto and it can easily split.
The solution can be seen in the next step.
Step 3: How to Put in the Middle Board
If you put the screws in from the opposite side of the board as shown above is the solution. The screw goes through the vertical board first then completely imbeds into middle horizontal board. This action can be seen in the three pictures above. Be sure to put a screw in from either side of the horizontal board to ensure maximum stability.
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.