Hammer Window Menu

From Valve Developer Community

This is a standard Windows menu. The only thing unusual is the Messages option, which will bring up Hammer's Messages window when an error occurs. The message window will report any problems Hammer had with loading its game configuration files. Typically, you will only see a message there if you have modified your .FGD file in some way and made a mistake.

The New Window function is useful for creating new windows when you're using independent window configurations.