Backup > Create Duplicate (File Menu)

This command creates a duplicate file of the current drawing. A file with the same name as the current drawing's file name but with the extension .DUP is created. This command can only be used if the current drawing already has a name.

If a duplicate file with the same name already exists, then a warning appears to avoid accidental overwriting of files.

Apart from the extension, a duplicate file is a " normal" drawing. They can be loaded as a duplicate file using the command File > Backup > Load Duplicate or like any other drawing using the command File > Open Drawing.

A duplicate file of a drawing should be created, for example, if some variant of the current drawing is to be tried out or operations are to be carried out which will change the drawing drastically and which can not be undone using the Undo command.