It is called verticutting because the blades are vertical as can be seen in this picture:
The verticutters are placed on a triplex and driven across the green:
Here is a close up look afterwards:
We go to a depth of about 1/8 of an inch:
In putting the greens afterwards I noticed an immediate difference in the improvement of the ball roll across the greens. Verticutting will be a weekly or bi-weekly practice throughout the Spring.