The \` command allows you to put text flushed right against any tab stop, including tab stop 0. However, it can't move text to the right of the last column because there's no tab stop there. The \` command moves all the text that follows it, up to the \\ or \end{tabbing} command that ends the line, to the right margin of the tabbing environment. There must be no \> or \' command between the \` and the command that ends the line.