All you have to do is drag the video you want to process inside the window, then set the number of rows and columns as well as the image resolution, background color, font, and a bunch of other customization options.
You can save the thumbnails in the most popular formats: JPG, PNG, BMP, GIF, and TIF. You can also process several videos simultaneously, saving a lot of time if you're working with episodes from a TV series, for example.
GDS Video Thumbnailer serves a very specific need and does it very well. Unfortunately, the watermark that comes with the trial version is quite annoying.
The trial version adds a very large watermark.