Starting a double sprang 
Before you start a double sprang you have to know some basics about sprang, as basic interlinking and making holes.
There are different methods of making a double sprang. I am using a method of working at both sides of the frame. With this method you use 2 safety cords. I like to have 2 different colors for this.

Fenny Nijman (from the book Sprang, Egyptisch vlechten) has made me a clear drawing of how to start a double sprang. I will share this drawing with you.



drawing start double sprang by Fenny Nijman
As you can see the blue thread is at the front of the frame, with the lowest safety cord and the red thread is at the back of the frame with the upper safety cord.
So your first thread (in blue) goes from under to above behind the lower safetycord and over the upper safety cord. Then it goes from front to back over the upper cord (or stick) and down over both safety cords and under the bottom cord (or stick), from back to front. Then the second thread (in red) goes from under to above behind both safety cords, from front to back over the top cord (or stick), over the upper safety cord and under the lower safety cord, and from back to front under the bottom cord (or stick). Now you continue with the first thread (now becoming your third thread) as in the drawing.

When all your threads are there you first put your hands in the field of your lower safety cord and you push to the top and the bottom, preparing your first field for spranging.
You also do this at the other side of the frame with the other safety cord. 
Now you are ready to start spranging at both sides of the frame. 
You can sprang a number of rows at each side and then bring all the threads or a part of the threads from the front to the back and from the back to the front. This is the most easy to do when you have made holes. Below you will find an example of the first steps in an experimental double sprang I have made. But recently I have made a more simple step by step tutorial for making a double sprang. Click at the link below to go to that tutorial.

Tutorial for double sprang.pdf

At the next picture you see both sides of the double sprang after I have done a couple of rows with holes at each side of the frame. Because I use very different yarns I have to do more rows with the thin threads to get the same height as the bold yarn.

double sprang after some rows at both sides
ATTENTION:  THERE WAS A MISTAKE IN THE FURTHER DESCRIPTION - I think I have corrected it now.
At side 1 I use an orange red safetycord and at side 2 a white safetycord.
Working at side 1 I alternately get one group of threads from side 2 to the front and push one group of threads from side 1 to the back. So the threads from side 2 come forward through the holes which are made in side 1.

From those threads that come forward I take the threads that are now in front of the white safetycord in my hand. Now I can replace the white safetycord.

Double sprang
When I have finished the first row after the change, I am not able to bring the new field down to the bottom yet. The threads are still trapped in the other safetycord. So I have to work a row at the other side of the frame now first.

trapped threads in double sprang
At the other side of the frame I pick up the threads that are now in front of the orange red safety cord. Then I can do one row of braiding and adjust the orange red safety cord in the new field. After this action I will return to the other side of the frame. Now I am able to push the new field down, starting at the white safety cord. After this I can start braiding at both sides until I again want to change colors....

double sprang
After some more rows at both sides it looks like the picture below.

Dubbele sprang

It is possible to repeat the whole process once again.... or do it a bit different.
I often use stitchholders for each group of threads. This makes it more easy to bring some groups of threads from the back to the front and other from the front to the back. This way I can choose to change only some groups of threads, while other stay where they are. 
Unfortunately I did not take pictures of this process with this double sprang....