Defence over

2♣ - showing either strong 2♣ opening or weak 2♦ opening

Overcalling or doubling on direct seat means, we are defending against strong 2♣ (ML)    ➲

After (2♣) - dbl - (2♦) we bid Rubensohl

To defend against weak 2♦ opening, we have to wait one round. Then:

dbl     =    12-14 , balanced, does not promise ♦ ST or very strong (later cue)

other   =    natural, 2NT = 15 - 18, ♦ ST