The example invention we are using to talk through the steps for writing a patent application is the Manfrotto mini PIXI tripod.
When you push the red button, the head can swivel. By releasing the button, the head position is then locked into position.
The user can quickly adjust the position of the head with the push of a button. There is no knob to rotate. Just push to adjust. Release to set.
The way that this works is with a wedge. More on this later, but you can see the wedge below. You can see that the left side is thinner than the right side.
I flipped the tripod upside down and removed the legs. From the bottom view, you can see the push button and a spring that biases the button out. This is the locked position. The thicker part of the wedge is closer to the button underneath the assembly shown below.
In the picture above, I removed two screws already. After removing the remaining two screws, I took off the assembly shown in the picture above. I’m holding the assembly in the picture below. You are seeing the underside of the assembly in the picture below.
When the button is not depressed, the spring pushes the button and a slider back to the locked position shown above. When the button is pushed in, the slider and the button are pushed in, as shown in the picture below.
The slider moves between the two positions as the button is pushed and released.
The slider and the wedge work together to lock the head of the tripod in place or release it so that the user can re-position the head as desired.
Upon removing the assembly, you can see that a spherical ball of the head is recessed within the wedge, as shown in the picture below. As will be further described below, the wedge is a part of the point of novelty of how the tripod works. Upon pushing the button and keeping it depressed, the head can be easily repositioned, then locked in place by releasing the button. 
I removed the wedge from the ball. See the image below.
The ball is seated within the semi-spherical recess of the wedge. To lock the head in place, the wedge is pushed upward into the ball. As you can see the lower half of the ball has ripples which increase the friction between the wedge and the ball when the wedge is pushed into the ball to lock the head in place.
Let’s talk more about the wedge. The wedge is shown in the picture below.
The left side of the wedge is shorter than the right side. When the button is released, the slider is traversed closer to the button side. The wedge is positioned so that its thicker side is closer to the button as well. The slider pushes in between the wedge and the assembly, and thus the slider also pushes up so that the wedge is not pushed into the ball of the head. The ripples in the lower half of the ball are frictionally held by the wedge so long as the wedge is jammed in between the assembly and the wedge.
When the button is pushed in, the slider is pushed toward the left side of the wedge. The left side of the wedge is the thinner side of the wedge. The slider doesn’t push upward against the wedge because of the extra room. Rather, the wedge is allowed to wiggle free so as to release the ball of the head.