Put To Library adds the selected material to the current library.
3ds Max opens a Put To Library dialog, which lets you enter a name for the material that’s different from the one you used in the Material Editor.
The material becomes visible in the material library display in the Material/Map Browser. The material is saved to the library file on disk. (You can also save a library by using the Save button in the Material/Map Browser.)
To save a material in a library:
The material is saved in the currently open library. If no library is open, a new library is created. You can save the new library as a file using the Material/Map Browser file controls.
The Put To Library dialog is displayed when you want to save the material in an active sample slot into a material library file. It lets you change the material's name before you save it.