Adapters with dovetail mount are used to attach a camera to a microscope eyepiece tube or phototube connector.
This connector as also known as V-mount.
The main idea is that such mount has inclined side. When you put it into other part, you should ring a screw (or few of them) that will pull the adapter toward the base part due to the mount inclination.
So, V-mount is improved version of a clamp connection in fact. Similar action, but much more higher reliability - you can not drop installed part with dovetail mount if screws got a bit loose.