Thumbtack grew out of a need to be able to manage many disk images at once while maintaining awareness of where they were mounted on disk. We further wanted to be able to automate the mounting/unmounting process for other tools to be able to process files on the images.
The Thumbtack server provides the backbone to be able to mount/unmount the images.
The Thumbtack client allows other tools to automate that process.
And the Thumbtack web interface allows a quick look at the mounted state of the images.