This is part of the Fake.IO.FileSystem module. FileSystemOperators Functions and values Function or valueDescription ( @@ ) path1 path2 Signature: path1:string -> path2:string -> string Modifiers: inline Combines two path strings using Path.Combine. Trims leading slashes of the right operand. This makes "/test" @@ "/sub" return /test/sub ( </> ) path1 path2 Signature: path1:string -> path2:string -> string Modifiers: inline Combines two path strings using Path.Combine