This is an older model of the Bigfoot Water Rocket Launcher. It's improved a lot since these pictures were taken, but the basic set up is simular.
This photo shows angle set for about 45 degrees. Rockets will travel 112 mph. Rockets will land about 600 feet away from launcher. One rocket is on the launch tube ready to launch, and the other two are staged on the top ends of the two angle adjustment legs.
Underneath the plywood base is a storage compartment for holding accessories. Presently there is room for 2 each angle adjustment legs, 3 each different length launch tubes for different size bottles, 1 each 20 foot pull string with handle, and a few other items.
See how the outrigger arms fold in and out for stability.
Here's another view of the launcher at about a 45 degree angle, but without the rockets.
View from side.
Sometime we get a little carried away, and pose a threat to all mankind.